I do find that most objections to porn come from younger people who tend to also be more insecure in relationships. Which is not a criticism. It's entirely natural for there to be more insecurity in relationships where both people are younger, haven't been a long term relationships, and are still learning a lot about relationships and life in general. I know a lot of couples in long term relationships (mostly in their late 20s and 30s) and I don't know a single woman who has issues with their other half watching porn. Indeed, a lot of couples have watched it together at some point and/or use it as part of their sex lives otherwise.
The main contradiction for me is that everyone agrees that porn isn't realistic, but then people call it disrespectful, morally wrong, equivalent to cheating and so on. In what way is watching something that isn't realistic something that amounts to cheating, disrespectful etc? For couples who are in a trusting, secure relationship, I'd suggest it can't be. Now don't get me wrong. Porn certainly can cause issues in relationships, mainly when the person watching porn has expectations that what they're watching can be reflected in their own sex life. Like anything, it can be viewed or used in a way that is unhealthy. And people are perfectly free to not like it or not want to view it themselves. But I don't see what is inherently wrong with it.