I dumped a guy because of the porn he wanted to watch. Was I justified?

You'd need to identify why he was watching it.
Is he homosexual. Does he care which men are in it as opposed to wanting to see the particular women (perhaps said favourite does a lot of that type). Is he woke and has white guilt. Is there a feature of it he likes.
Without a conversation with him I don't think one can draw too many conclusions.
You were certainly justified if you don't like his sexual tastes but over the years a man's sexual taste in porn change even if his RL tastes have stayed the same.
I've rolled through a few months of different types before I move on but my RL tastes have remained identical. Porn is not real to me so I view it as no different to how I watch a lot of sci-fi for a few months then a lot of period dramas.
So basically, ask him why and identify whether he just likes particular porn stars, whether it's an always thing or just recent or whether he's got white guilt and wants to be cucked.

He said a few things like "liking the contrast" and stuff but he got quite embarrassed when I tried to get into it. He hinted at how he imagined me as the girl in the clip and found it so hot. As in he really liked the ones where the girls were blonde and otherwise looked like me.
What exactly do you mean by white guilt and cucked? What is he feeling guilty for and what does that have to do with it?

It's a tad strange that he spoke of contrast because that implies that he does value the men in it (for me, the man is an irrelevance in porn, penis aside). The later statement is natural and not a bad thing (I'm sure it would be worse for you if he was looking at women nothing like you).
Essentially there's a segment of weak, submissive men who allow racial dynamics to be sexualised. One can't expand too much here.

I recently broke up with a guy I had been dating for a few months, and who I thought things were going well with, because I saw the porn he was into and I just wanted peoples thoughts as to whether I overreacted or not. I'm not against porn, though I understand why some people are, and it's usually not a big issue for me but for this guy it was the type of porn he was watching.
Bearing in mind we are both white (we live in a rural and very white part of the UK) he was watching essentially exclusively interracial porn, where the women was white and the man was Black. As a white man, why would you exclusively watch that? I thought the whole point of porn was imagining yourself in the scene, but the guys in the scene are literally nothing like him (though many of the girls had my features.)
I've never really watched this kind of stuff before but he was watching stuff from studios like Blacked dot com who I think only make stuff with white girls and Black men and where it focuses on how "Black guys are better" and situations where they are stealing white guys girls.
It's not that I didn't appreciate the scenes (To be honest some were super hot. I've never even thought about Black guys in that way but it's made me very curious!) but it was the fact it was that my white boyfriend liked them was a huge turn off. I don't want to sound mean but it made him come across as so weak and passive.
Am I completely overreacting? I can't help how it made me feel. Is it at all common for white guys to be into that kind of stuff? Why?

Personally i find it more interesting that you didnt like him watching sex that involved non-white people. What does it matter if the man was Asian, Black, White etc? Should only a Black man watch that porn? Sure there are power dynamics at play, but that is the same for most porn.
Porn is not always a direct representation of reality or undisclosed urges, people are curious about differences and unusual situations also, otherwise there would be a lot more pizza boys out there.
Greg

Can I ask what it was you liked about seeing the Black guys? I've seen Blacked so I know which guys you mean.

Most porn is pretty vile and there is something about making interracial a thing and stereotyping that is at least distasteful. Whether or not it’s worse than other things that are regularly watched is another matter. Anyway if it didn’t work for you you’re within you rights to draw a line on it

I recently broke up with a guy I had been dating for a few months, and who I thought things were going well with, because I saw the porn he was into and I just wanted peoples thoughts as to whether I overreacted or not. I'm not against porn, though I understand why some people are, and it's usually not a big issue for me but for this guy it was the type of porn he was watching.
Bearing in mind we are both white (we live in a rural and very white part of the UK) he was watching essentially exclusively interracial porn, where the women was white and the man was Black. As a white man, why would you exclusively watch that? I thought the whole point of porn was imagining yourself in the scene, but the guys in the scene are literally nothing like him (though many of the girls had my features.)
I've never really watched this kind of stuff before but he was watching stuff from studios like Blacked dot com who I think only make stuff with white girls and Black men and where it focuses on how "Black guys are better" and situations where they are stealing white guys girls.
It's not that I didn't appreciate the scenes (To be honest some were super hot. I've never even thought about Black guys in that way but it's made me very curious!) but it was the fact it was that my white boyfriend liked them was a huge turn off. I don't want to sound mean but it made him come across as so weak and passive.
Am I completely overreacting? I can't help how it made me feel. Is it at all common for white guys to be into that kind of stuff? Why?

Most porn is pretty vile and there is something about making interracial a thing and stereotyping that is at least distasteful. Whether or not it’s worse than other things that are regularly watched is another matter. Anyway if it didn’t work for you you’re within you rights to draw a line on it

Are there any actual truth to the stereotypes?

"I thought the whole point of porn was imagining yourself in the scene"
There isn't any real significant point to watching porn. In the same way that there isn't any real significant point to watching Hollywood action films.
If someone enjoyed watching Avatar films (all 2 of them) you wouldn't say that they liked imagining themselves as blue giant cat people.
If someone enjoyed watching Dune films, you wouldn't say they wanted to imagine living in a desert, nor riding giant sandworms.
It's just entertainment.
And sexual fantasies can be a highly personal and a weird or warped thing. It's just the way human minds can work. Check out the Nancy Friday books for plenty of examples of sexual fantasies.
Thinking and fantasizing about something is one thing. Actually doing it is an entirely different kettle of fish.
Having said all that, it's down to your boyfriend to motivate you to stay with him. If he hasn't done that sufficiently you're quite right to dump him.
I think that a guy that had watched some porn and never really gotten into it, mainly because he had too much other worthwhile stuff going on in his life would be more suited to you.
"Most porn is pretty vile". What sort of porn have you been watching?
The porn that I've watched was generally somewhat comical in how time after time it stuck to certain porn conventions.
With it getting quite boring after a while.

Well, it's all a bit lewd to talk about, but obviously their size. Both down there but just in general. I can only imagine being with a guy that big would make me feel incredibly soft and vulnerable (which can be a huge turn on when done right). And I love how dominant and confident they are.
There is an aspect that coming from a pretty traditional family and a pretty white area it's also... well... all a bit taboo. Which just makes it hotter haha

It depends which stereotype you are talking about but there's little statistical evidence to back the one your probably thinking of. Most people who enter porn are abnormally gifted genetically (although some have enhancement operations such as ligament or filler). There's also a lot of camera tricks and many porn stars are absurdly tiny (women who are petite and 5 foot, men who are actually quite short so everything looks larger in proportion).
Basically, according to Meta studies of the data (academic studies of multiple academic studies) found that 95% of men globally are between 3.9 and 6.5 and the only weak correlation they found was height so tall men are a bit more likely to be holding a cucumber but not by much (and actually the Dutch rank tallest I believe).
So in a word, no. It's largely a myth that stems from the US plantations slavery where gifted men may have had their way with the wives and daughters. It didn't prevent most of the slaves being unexceptional.

I assume the vile stuff refers to objectification or porn addiction.
I tend to agree with you personally, I have no qualms.

"I thought the whole point of porn was imagining yourself in the scene"
There isn't any real significant point to watching porn. In the same way that there isn't any real significant point to watching Hollywood action films.
If someone enjoyed watching Avatar films (all 2 of them) you wouldn't say that they liked imagining themselves as blue giant cat people.
If someone enjoyed watching Dune films, you wouldn't say they wanted to imagine living in a desert, nor riding giant sandworms.
It's just entertainment.
And sexual fantasies can be a highly personal and a weird or warped thing. It's just the way human minds can work. Check out the Nancy Friday books for plenty of examples of sexual fantasies.
Thinking and fantasizing about something is one thing. Actually doing it is an entirely different kettle of fish.
Having said all that, it's down to your boyfriend to motivate you to stay with him. If he hasn't done that sufficiently you're quite right to dump him.
I think that a guy that had watched some porn and never really gotten into it, mainly because he had too much other worthwhile stuff going on in his life would be more suited to you.
"Most porn is pretty vile". What sort of porn have you been watching?
The porn that I've watched was generally somewhat comical in how time after time it stuck to certain porn conventions.
With it getting quite boring after a while.

I know it doesn't always work that way but my bf really seemed to enjoy the idea he was just watching. He liked one of the scenes where the Black guy 'stole' the White guys gf and he really liked the scenes where the girl looked like me and he hinted at how hot it would be if he was watching me.
I guess that can be exciting (and to me being with one of those Black guys would be really hot) but it made me perceive him and really weak and kinda creepy at the time. I get that it's voyeurism? Is that right? But it wasn't an attractive thing for him.

Sounds like he might be a cuckold.