I had no idea what Kiwifarms was until Christchurch. The mainstream platforms basically invite people to go to platforms concentrated in more extreme speech by deplatforming legal but controversial speech. IMO it is more beneficial to have mainstream platforms with all manners of free speech than to concentrate extreme speech in certain locations where it becomes normalized without the benefit of mixing in more mainstream opinions. I would not be surprised to find out censorship and moderation results in increased radicalization, etc by concentrating controversial ideas in these 'extreme' platforms rather than mixing them with more moderate ideas.