It should not be up to Matthew Prince to decide who to block. He has demonstrated his inability to function as censor in a very visible (and frankly embarassing) way.
How? There have been exactly two cases of "censorship", and that is the Daily Stormer and 8chan. One is an utterly vile peddler of antisemitism (literally named after a Nazi paper) and conspiracy theory, and one was linked to at least three terroristic attacks. If it were not white supremacists but Islamists, it would be closed down in an instant and no one would bat an eye.
If anything, Cloudflare seriously lacks (like Facebook and Twitter) policing their customer base.
This is ironic since Cloudflare has famously been under fire because Prince specifically decided against removing ISIS websites from Cloudflare and vehemently defended his decision that Cloudflare should not be censoring anyone.
Prince himself even agrees with the parent comment, and he goes into pretty good detail in his blog post here [1] about why companies like Cloudflare should not be able to make the decision to remove websites, and that it should be left up to governments. I guess he got overruled on that stance when it came to 8chan, though.
1: https://blog.cloudflare.com/why-we-terminated-daily-stormer/