The comments immediately go in to decrying anonymity. This seems precisely backwards to me: Yes, even some mentally ill persons will be less hesitant to behave abusively under their legal name. But many will not, the examples given are people who are behaving abusively in part because they've adopted the abusive conduct as an identity. They aren't ashamed of it.

Worse, a lot of the damage these people can do depends on knowing their target's identity. If some internet nutbar gets overheated in an argument and starts slandering you with random accusations but you're only known as a pseudonym then at worst you can abandon the pseudonym. But you probably don't even have to go that far: without knowing more about you its hard to make accusations that are even credible enough for an internet hate mob.