[Ottolay]

Maybe because it's not an axiomatic fact. There has been niche radical internet communities for ages. It has only been with the radical communities coming into the mainstreams ones (reddit, twitter, and facebook)that the radical communities exploded.

[saurik]

I think the idea is more like this: you have two clubhouses, one that has 10 super radical people and one that has 190 people who are less radical. If you take the most radical 20 people from the 190 and force them to go across the street and spend all of their time with the super radical people, those 20 people probably will become somewhat more radical. Now, the 10 people possibly become slightly less radical as maybe do the remaining 170, which might balance things out a bit? But the people who are saying this makes people more radical are concentrating on the idea of taking people on the verge of being super radical and saying that they now only get to hang out with each other and the people who were thrown out of the mainstream long ago... it isn't that that group will "grow" past the people handed to it, but that the people given to it will become radicalized (which might be more dangerous than accepting everyone into the same system and attempting to have them all adjust a bit towards the mean).