The rules of society are always a trade-off.

In this case, the idea is to lose a bit of free speech, and gain less hatred and less murder. That is not an arbitrary judgement; admittedly this is also not a clear-cut judgement.

The system never works itself out, successful societies are the ones which have established governing rules. Game theory has given us pretty good indication that systems rather self-destruct without governance than self-stabilize.