But why is making a (racial) caricature of someone harmful? Can you imagine any situation or alternative timeline in which such a caricature would be neutral?

It was not created in a vacuum

I think that non-vacuum is exactly what I'm getting at. Was it created it to be racist? Was it used to promote a negative image of people? Minstrel shows certainly were used that way, but I don't know that Zwarte Piet was.

I'm not being "willfully ignorant" - I just disagree about something and am trying to give you the space to convince me otherwise (but it's up to you if you don't want to follow that thread any more)