There is a certain "jurisprudence" to this sort of thing. All laws are written ambiguously; that doesn't mean it's impossible to enforce them or that the laws are useless. Human interaction shouldn't be codified into computer code and in most cases can't be.
Whatever Twitter decides those things are, someone will be upset about it, and someone will contest the definition. That's fine. We already have this kind of thing in HN and Reddit and anywhere else on the internet where any kind of moderation happens. We had it in Usenet and in web forums.
The whole idea that ambiguity in the laws means that we should have absolute "free speech" including the demonstrably toxic and hateful place that Twitter has become is bonkers. Sure, you'll alienate some people who don't like your definitions. But that's kind of the point. To foster the community you want to have.