So I am going to go out on a limb here and assume that you are a sensible person, who is genuinely asking this question, and NOT some kind of neck-bearded, tribalistic troll, who cannot see past their own opinions.
Because I think you are a reasonable person, I will try to share, what is arguably a "correct" answer (or at least one that is as correct an answer as can be given to an opinion-based question, which in turn has an opinion-based answer).
The reason why there are so many VOCAL haters is that the internet in general and these forums in specific tend to act as a filtering mechanism, which only displays a small portion of a complete data set while giving the impression that said small portion IS a complete data set.
What I mean by that is, that most moderate people who are either for/against a topic simply don't post. They may say "That's cool" "Another NTR game... blah" or something similar, but the reality is that they don't care enough to voice their opinion either way.
What this means is that the majority of posts you see (specifically those discussing a kink such as NTR) are from the people who meet the two qualifiers of 1)Having a Strong Opinion and 2)Having a Strong desire to share that opinion.
Combining this basic premise with the fact that forums such as F95, only shows the data points (in this case 'opinions') which are written, and don't (read cannot) show those opinions which are 'not written'. Then add in the fact that the base numbers you are filtering this through start with the vast majority of people either have a negative or neutral view of NTR as a kink, and the result is a perception that there are (as you put it) "so many vocal haters".
To put into an example;
- Chad Morecock doesn't like NTR (or incest, femdom, or whatever), so Chad makes a point of pressing the 'ignore' button every time a "Whatever Tag" game comes up on F95.
- No one, (except maybe some Mods, or back-end data collection) see's that Chad has "Ignored" Dozens of "Whatever Tag" games over the last year.
- What forum members DO see are the times that Chad posted how he was disappointed that a game added or had "Whatever Tag", complained that a tag was missing, or made some otherwise negative comment about "Tag".
The result is the perception (from the viewpoint of forum readers) that Chad is an NTR (or Whatever) Troll/Hater. Though from Chad's own viewpoint, he generally just presses 'ignore' and moves on, only commenting on the rare occasion.
A couple of qualifiers;
-This doesn't apply to Trolls in general, of which there are many, and (like the majority) are statistically more likely to be NTR negative, or neutral, with the usual understanding that the more extreme an opinion gets, the more vocal its holder becomes.
-This also doesn't take into account that in general, the internet is anonymous and as such free of most consequences, which has a plethora of psychological effects on methods of interaction.
-English isn't my first language, and I have drank like two bottles of wine at this point, so I maybe am botching up this explanation.
As a final thought, it would be interesting to see a data point (like the reviews for each game) that showed how many people "Ignored" a game, and for what reason. Then compare that to the number of people who post comments like "I am ignoring this because of ... bla bla bla"
Anyway, there is one Frenchman's somewhat drunk, somewhat educated answer to your question...