Once someone sets up their "private property" as a public forum, they're on the spectrum of operating as a de facto government. If there were ideological competition between reverse proxies like Cloudflare, the "private association" argument would have weight. But rather Cloudflare seems to be acting due to pressure from an concerted effort to implement censorship across every such business.

No one argues against the right of a company not to host Nazi forums. But there is an ongoing trend were companies that wished to be apolitical are forced into political decision.