I think Zwarte Piet is racist only when seen through American lenses. Which unfortunately today is the norm, but that doesn't make it more sensible. Zwarte Piet is basically Santa's little helper, as they exist in many traditions. He's black so he's represented by people with their face painted black. The fact that blackface has a connotation of racism in a country where racial laws where abolished only in 1964 has nothing to do with the substance and meaning of a Dutch Christmas tradition.