I don't know about that. I'm as big a defender of the First Amendment as you're likely to find - I'm firmly on Jack Phelps side, and I'm even open to the idea that certain tech companies are moving from "providers" to "editors," so if you can sell ANYONE on this you can probably sell me...but I gotta say, I have no problem with Cloudflare terminating its relationship with 8chan. Frankly, I don't see the connection you're trying to draw.
Cloudflare is not saying 8chan can't be 8chan. It's just saying that it doesn't want to be involved with 8chan anymore. Fair enough. Nor are we looking at a Facebook or Twitter situation here, where one company is SO big that it effectively controls the venue as a whole. Cloudflare has many competitors....even you acknowledge that 8chan will have minimal problems finding a new home.
So everyone is happy. Cloudflare makes a statement, 8chan gets a new home, and First Amendment issues simply do not apply.