The "people are better behaved with their real names" argument is bunk. And we don't necessarily want people to be better behaved. I don't care much if HaXXoR15 is rude, because I can just block him.
What I do care about is HaXXoR15 creating hundreds of sock-puppets to escape banning. And I worry a lot about spammers creating ever-more-sophisticated fake accounts and fake networks in order to flood services with their messages. And this is the thing that pro-psuedonymity people really don't seem to tackle (though, to be fair, then anti-pseudonym camp really hasn't stressed it enough either.)
I don't care what you call yourself on the Internet. I do care that whatever mechanism you use for generating psuedonyms and building reputation for them can't be duplicated and exploited by spam-bots and hordes of Mechanical Turk workers. Tying an online identity to a real identity is a very crude way of accomplishing this. (Banning people for unusual names is not.) I don't have a better solution ready at hand, but I think we need to admit that "unanchored" identities can be a threat. I don't want Internet "driver's licenses"--- what a nightmare--- and they wouldn't stop botnets from using the identities of the computers they reside on. But the ability of bad actors to impersonate real people is only going to increase.