As I tried to explain a couple of times. We don't see it as slavery. People dress themselfs like moors. Not slaves!
If that's an insult then it's an insult to dress up like any race.
People can dress like a moor without having black face, big red lips gold earrings and stupid voices. it's these additions to the dress that kind of make zwarte piet look a bit like a....... if it's soot on his face whats with the black curly hair, dark black skin, gold earings big read lips and stupid voices very similar to other stereotypical racial images.
Given the history, the orignal book and the current debate, yes i fail to understand why black face is needed. nothing personal, i have many dutch friends who are for and against, no hard feelings.