On the specific costume, if deliberate (which it probably would be), there are other rules that would come under besides direct harassment.
in any case you've flipped your example around and are trying to claim it's the same thing.
The
first time, you were talking about giving someone the ability to turn off an "offending man in a dress" that they are personally unable to tolerate. Not because they are trying to harass the person but simply because they are wearing a dress, and somehow (according to you) if the other person "lashed out" it would be the fault of the so-called offender and not the one expressing bigotry.
Now you're talking about someone dressing up as a commonly-identified racial hate group (which, without actually checking, I would assume is prohibited in the TOS, if not actually illegal) and equating it to the same situation, which it is not. It should not be "quietly turned off" and a moderator would probably tell them to change their outfit even if the player claimed they had no idea it was offensive - whereas they wouldn't just because a male character has equipped a normal piece of clothing that their character is able to equip.