Critical thinkers know trying to censor extremists tends to make them... more... extreme...
It does yes. Those few users still willing to go the extra mile to use the site will become more extreme in their views as the worst opinions are echoed in a smaller group with fewer dissenting opinions.
On the other hand, the added difficulty of getting to the site, and it's disconnection from the 'normal' internet means it will be harder for the site itself to recruit new users to it. This in theory means fewer people who are vulnerable or susceptible to those views will ever get to the site and be inducted into that echo. However, there are still plenty of other communities on the regular web which are already echo chambers for the same views and these will continue to direct potential recruits to 8chan and instruct them on how to get to it.
It absolutely makes sense though why Cloudflare would not want involvement with the website, but as they say, they aren't fixing the problem as a whole.