4chan has a lot less extremism than people imagine, rspecially compared to platforms like Instagram or Facebook. It's mostly concentrated on certain boards. The reputation of being extremist did more 'in favour' of its extremism than the original userbase and design ever did.
4chan is only outdone by 8chan. “It’s only concentrated on certain boards” is the same lame excuse Reddit used to ignore /r/thedonald and now /r/conservative.