If you turn "I only have sex with women" into "I only have sex with white people", suddenly it sounds pretty offensive. Can we judge those two statements equivalently? It's not a good argument at all.

> It's a very good argument.

In the best case, that argument only has a little utility. However, it's a pretty bad argument now, since political correctness only allows you to make those kinds of swaps in certain cases. Nowadays, it can only be use to amplify the outrage against an already-identified villain.

I think there's a different point -- that we're willing to ignore certain avenues of discussion to maintain a civil society.