This is the thing, the balance of anonymity and preventing people using that anonymity to be a tit.
In my opinion, one of the answers is keeping the signal-to-noise high: Make sure that there are enough sensible people in a community that if someone starts acting up, they're alone. And then they can either correct their course, or get banned, ideally before the next moron shows up.
And part of the way of achieving that is raising the barrier to sign-up, if only a little, and rate limiting.