Nobody would ever say that though. Is there anybody who would argue that anonymity is only used for good? You set up a strawman and made a point against it.
Anonymity is a very important aspect of discourse. Just ask Silence Dogood... Actually, Richard Saunders... Er, Anthony Afterwit... I mean, Polly Baker... Benjamin Franklin.
I'm not going to support any attempts to curtail it. Anyone operating a forum for discussion can run it however they wish of course. Which leads me to the rest of your post which seemed to be more about censorship/banning which isn't really the same discussion. I'm very much against that as well but an operator can censor without removing anonymous/aliased posting.