That's not what was on kiwifarms. I've read that odious forum for years and their whole shtick is, "Look but don't touch." They do gather identifying information, and they do archive what people have said and done, but the moderators heavily discourage users from interacting with any of the "lolcows". Doing so is one of the few things that will get you banned from the forum. If you want to attack a site that does encourage physically threatening people, then you'll want to go after places like doxbin. That said, I disagree with Cloudflare's decision (especially since they still provide services for godhatesfags.com and host copies of ISIS's English propaganda magazine), but I don't think there should be a law forcing them to provide services to kiwifarms.

But to get at your point about legality: the definition of a true threat is quite narrow. In Watts v United States[1], a draft protestor said, "If they ever make me carry a rifle the first man I want to get in my sights is L.B.J." The Supreme Court deemed that threat to be legal under the first amendment. Posting someone's address (which is already public info in most tax records) is usually unethical and immoral, but it's not a crime and I'm fine with that. There are many immoral acts which are not criminal, such as cheating on one's spouse or lying about serving in the military. We can use other methods to discourage such behavior (such as shunning). Passing a law against something means that men with guns will come to people's homes and put them in cages. That's one hell of an escalation, and I'm not willing to endorse that unless the perpetrator is extremely dangerous.

1. https://www.mtsu.edu/first-amendment/article/707/watts-v-uni...