The purest forms of evil that we know about predate the internet. Not to mention, removing anonymity also removes a real resource for individuals.
I was depressed a lot as a young person and considered suicide. I’d never share these feelings offline. Online, I was able to connect with individuals that I can speak truthfully to.
Also, anonymity makes me take every post at value. For example, if you’re biased against a religion, political affiliation, race, etc, you might find that you ignore posts made by those you’re biased again. Anonymous posters don’t have this worry - I don’t know who you are. Thus, the only thing I can judge is your words. Not past words, but words here and now.
There’s positives and negatives but in this case the negatives far outweighs the positives.