Seriously.
If you want to run a forum that censors people you disagree with, FINE. But do it in the open.
Say up front: "We're going to allow some people to use some words, but other people can't."
Don't be coy. Don't be shy. Don't pretend like it's out of your control.
Just be up front about it.
And tell people, "Hey, you can say fucking nigger" all day long, but because you didn't pay us or whatever, you can't say "lie".