Do you understand that two things can be true at the same time even though they sound like they're opposite to one another? It's entirely reasonable to assume that places like that both prevent many people from falling further down a hole of exclusion but also push others further inside.
Their further fall into exclusion is stopped, because they are echo-chamber bubble that pushed them further into hate.
Social isolation does not make you extremist on itself - contact with extremists that recruit you make you extremist. Social isolation make you more vulnerable to extremists.
And how many mass murderers were not linked to any online forums or they were so crazy that they got ostracised even on the most extreme forums?
Three is just a number if you don't know the sample size. If it's 3 out of 3 million and the US had 600 mass murderers out per 300 million population then 8channer is twice as safe as average Joe. (Made up numbers to illustrate the math).
