Especially for Americans this must be so blatantly obviously racism, it's kinda embarrassing for people who are aware of international sensitivities, yet their own country is completely oblivious (like me, I'm Belgian).
The vast majority of dutch/belgian people simply don't see the skin color as an issue. I'd say that makes it more ignorant than racist. I as well just grew up with the idea of an old fart in a saints suit coming once a year to give presents to children, helped by a bunch of black guys in weird outfits entertaining the kids and giving out candy. I think, hope, that this tradition hasn't affected my attitude or underlying feelings towards black people. Hell, there is this popular tv show about Sinterklaas and Piet where Sinterklaas is basically a grumpy, childish, senile man, whereas Piet is lively, lovely, has a sense of humor, is smart, ...
But still, if you take a look back at the tradition, I mean...come on. It's racist as fuck. Old man with black helpers. Just change the damn tradition already: give the Pieten all colors of the rainbow for all I care, or just don't paint the faces, but just change it already because the racist aspect is clear, and it's upsetting quite a lot of people.
The Sinterklaas tradition has been changed a lot throughout the decades anyway. It's always happened organically/spontaneous. It's just that now some people want to force a change (rightfully so), that there's a vocal opposition against it (not surprisingly).