I think its because society is gradually becoming more progressive, those on the fringes are lashing out and are very active on the internet as its a place they can hide and be anonymous.
In real life, if you start spouting off views about how much you hate Muslims, gay people, women, other races, poor people etc then very quickly people are going to think you are a knob. Now these people like to paint themselves as bastions of free speech sometimes by saying you should have the right to say what you want and we live in a censored world etc but actually there aren't as many laws against this as they make out. A lot of the time when someone in the public eye is forced to apologise/resign because of saying something controversial on the lines above, it's not because of any threat of legal action, it's because they get public backlash from people exercising their own right to free speech.
The implication for all the people that have those racist/homophobic/misogynistic/anti-Islamic views is that they have soon learned they can't express them in real life to people around them because they will soon lose friends. Some of these people are completely obsessed by it - you can see on internet forums like this how they start multiple threads over and over again about the same issue (usually against Islam or feminism), it is something they think about all the time. Can you imagine hanging around someone that was always talking about Islam/feminism 24/7 you would just think they were the most boring/weird obsessed person ever. If they did it in real life they would soon have no friends and be seen as a loser.
So they get forced on to the internet where they can hide their true identity and talk about it and also thats where they will find the other people that think like them who can agree with them.
TSR is not unusual to be saturated with these type of people, it's what the internet is like. Look at youtube, any video that has a significant number of comments will soon turn in to an argument about race/slavery/Ku Klux Klan or Islam v the West. Also if you find any forum that caters for a niche interest (sport, a hobby etc) if they have an 'off topic' or 'politics' subforum it is like TSR, you get some obsessed posters posting continually about how much they hate Islam or how feminism is destroying society.
Now if you look at the internet as being representative of society you can get a view that disappoints you about society but it's actually the opposite situation - the people with these kind of aggressive views feel marginalised because most people today don't agree with them in the way that in the past they might have done so they resort to being more active online.