It is racist. You cannot argue otherwise. The origin is racist. The character depicted is a racist caricature. The image is entirely and completely racist. The question is really whether the Dutch are tolerant of this racist imagery. And yes, they are.
Sure I can argue otherwise.
Although I agree that the roots are racist and that outsiders can easily interpret it as racist I argue that it isn't racist.
What is racist about it?
That white people where blackface? Not really a thing here in The Netherlands. I understand that is a big big thing in the US, but we didn't have those same problems in the same way as you guys. So different culture.
That he is a helper of Sinterklaas and is black? Not really a problem. People don't see it as a white guy calling the shots. Slavery was not a big thing in The Netherlands themselfs so we don't make those connotations. We probably did terrible things in Africa and Asia, but here it really wasn't a big a thing as in the US.
For all we care Sinterklaas was black and Zwarte Piet was white. It doesn't really matter. What matters to people is the change, why change stuff? To cater to foreigners who have a different cultural background who project their own racist history on our society?