That handful of people you find on a forum more devoted to whatever the topic or niche is than everybody else. The people that are there, every day all day immersing themselves in it.
They're fairly far and few between and wherever you are, you'll find a handful of them.
The rest of the more vocal people tend to be the 'hanger ons'. The ones that are into it as long as a bunch of others are, but will lose interest if the community fades.
Then there's the flyby people. The people who just kinda pop in from time to time, but aren't really all that into it.
People seem to forget, we call it 'extremism' because it's at the extreme end of what humans consider acceptable. Most people in general are not 'extremists' with anything otherwise we wouldn't call it extreme. It would just be normal.
Everyone seems to just label someone as an extremist for a tweet, or an idea, or some words, where in reality a good majority of people being labeled as such are more than likely just normal people saying some dumb shit.
Everybody's done it, nobody's perfect anywhere, everybody believes ridiculous things from time to time, everybody's said things they shouldn't, it's just a part of being human. It doesn't mean they're this, that or the other kind of extremist.