Anonymity wasn't why the 4chan hate machine would fire up--it was because a few people could look like a lot of people. It looked like you had a mob right at hand.
Hmm, that's an interesting take. I always thought it was the "I can say whatever and they'll never know it was me, mwahaha the perfect crimeeee!" or something.
Now, there are a lot of people, and bots besides.