You know how in the US they aim to remove everything about racism, black history and rewrite native history in many states? This is one front of bigotry. Another one is to remove the visibility in arts and culture. One angle is to remove and supress works created by people from minorities. The other is to remove minority characters from works of fiction.

And at the end of that culture war, when the "ideal" mainstream society is created in the heads it is creates in the real world by persecution of the excluded minorities.

And while the modder has the right to mod how he sees fit, it is perfectly justified for the platform to not help him distribute it. And in such it is different from mods turning mainstream characters into minority characters because it has no negative consequences for peopledown the line.