Additionally, being charitable is a privilege of the well-off white man. Minorities don't get the same extended to them. It's hard to be charitable with people who want you to not exist. It's easy to go "woah woah let's have some calm and charitable discourse here" when you're not under attack daily through systematic and otherwise bigotry.
I've always loved this argument. "There's too much bigotry in the real world, therefore i am
compelled to be a shitty person to interact with on an internet forum."
If you want to angry shitpost just do it on Twitter or 4chan. A forum is supposed to be conducive to discussion, and frankly the entire idea of moderated forum discussion is invalidated by bending the rules to a privilege hierarchy.
Every decent forum I've ever been to has had something the along the lines of Rule #1: Don't be a dick! And here is Nynt9 arguing for exemptions.