Before thinking about passing anti-online-abuse legislation in all countries (which, like you, I'm not very sure would be effective), we should first agree that

Before thinking about passing anti-online-abuse legislation in all countries (which, like you, I'm not very sure would be effective), we should first agree that online abuse is actually a bad thing, with real negative consequences. Then, we can figure out what we, as individuals, can do to alleviate the problem, like ceasing any sort of collaboration with a known abuser (just an example; haven't thought it through).