To me this not so much about the name that is displayed publicly, but about the fact that if you allow someone to publish on your platform, you should have proof of their identity, so that you can hold them legally accountable for their actions. At least in Germany hate speech, defamation, harassment, incitement to violence and so on are actually prosecuted and proof of identity would make that prosecution much easier (and yes I understand that there are different standards for speech in the US)