Yes, it's the anonymity, and knowing that whatever you say has virtually zero consequence. But I can honestly say that with all my posts and all my future posts, I would say them to people's faces in person. The venom that is mostly spewed is ad hominem (see youtube comments for the worst of the worst).

I hope this place stays as far from youtube comments as possible. Let's all hug!

and that's why i don't comment on youtube