Recently Reuters and other US & int. media picked up a story about Black Pete being a form of racism or even blackface. As most in The Netherlands and Belgium and the North of France know this is incorrect.
Zwarte Piet / Black Pete represents historically not a helper or a slave, but a Moor. Sinterklaas, a bishop, is from catholic Spain (Spain occupied/ruled the south of The Netherlands long ago. )
Sinterklaas, Saint Nicholas, is not really from Spain, but Spain became center of the catholic empire who ruled The Netherlands during the medieval occupation and so the city in the legend of the Sint changed from Mira to Madrid. (Sidenote:Sint and Santa are the same )
Sinterklaas gives presents, Black Pete historically punishes bad kids, but is in past decades along with new views about parenting and tv become a far more friendly figure.
Black Petes are Moors and were not slaves. They, Islamic jihadi’s, conquered and occupied Spain until the reconquesta (see painting), hence the black and historically even devilish representation in the eyes of what was once a catholic tradition. White vs Dark, Good vs Evil, Europe/Rome/Spain vs the Moors. Rewards gifts/sweets (sweet chocolate and pepernoten) for good kids vs the (fake) promise of punishment (salt, roe, put in sack to be taken to Spain, not anymore) for bad kids.
Update: Dutch article from the Volkskrant http://i.imgur.com/JEsMayk.png
More information: Meertens Inst. (in Dutch)