As someone who was a long time user of 4chan and that believed this once before, I now adamantly disagree that total anonymity leads to better discussion and believe that 4chan and the like are ultimately failed experiments.
With total anonymity you end up with trolls or people who are just seriously misinformed arguing vigorously.
You can spend the time and present arguments to possibly convince an actual reasonable person. It gets tiresome over time posting the same basic information. Most of the boards on there end up with a good baseline of information for their topics over years, but for anyone slightly knowledgeable it is tiresome to move topics to that eventual baseline and especially to move them past it. That same information can usually be collected from less toxic sources in a few months as opposed to years that the collective takes.
Every once in a while you'll get a fresh expert that hasn't gotten tired of posting the same information, but I stopped years ago bothering to share any information I had. It's always an up hill battle and the posts will be gone in a few hours or, at best, days
But trolls end up dominating. If you waste your time writing informed sourced posts about anything (slavery is bad, the Holocaust happened, Earth isn't flat, etc) all that will happen is the person will eventually just criticize basic grammar mistakes, insult you, and post the same garbage in a new thread.
If you make the mistake of arguing with organized trolls, you'll get link bombed with shit sources and barely tangentially related long sources that suck up your time before you realize that they don't present any facts that are actually relevant to the discussion.
Even 4chan knows this. The business board has measures in place to inform readers when a poster is the same person.
Real names are not needed online to have good discussion. But it's absolutely needed for posters to have repercussions for past posts. True anonymity leads to shallow discussion and trolls.