This is the equivalent of a forum on black rights allowing a KKK member that simps for Rhodesia and Apartheid South Africa to post.Does ignoring him stop him from posting? Because that's really what is being asked for here.
The way I see it, there's only two ways to do it: The easy way and the hard way.
The easy way involves banning him. And when he pops up with another username, ban him again. The dude clearly isn't capable of alternating his posting pattern, so regardless of what IP he uses, it would be easy to identify him. And if the main forum mods don't want the work and the headache, I'm sure there are plenty of volunteers who would be happy to at least police this thread or any of the non-flagship threads.
The hard way involves inviting this guy for tea, and all the complicated logistics therein.
I'm honestly ok with either method. In a perfect world, I would much prefer the latter than the former. But we don't live in a perfect world, and as cathartic as it would be, he's not worth the effort of the latter.
Would even white members of that forum say "well we want to be tolerant to different viewpoints" or "a forum on black rights isn't necessarily a black people's forum"? Would they dare even suggest it?
If changing the wording of Chinese to black makes one feel uncomfortable then it is racism to use Chinese there too. Simple as that.