The celebration of this day starts about a month before the actual day and during this time you see these kind of things:
Black Peter (Zwarte Piet)
Santa Claus (Sinterklaas)

As you can see, these are white people where black and brown make-up. These Black Peters also tend to be loud, dance around and/or they do acrobatic moves. Some black people find the party offensive, racist and have tried to get it banned. Meanwhile, as a turist you only see this when you leave the airport. I have never seen any Black Peter or Sinterklaas at the Schiphol Airport, which leads me to think that it is forbidden to show these "cultural elements" in international areas.
In my opinion the Black Peters are in fact offensive; the black make-up, kinky wig and fake big red lips are self-explanatory. Still, as long as I don't surround myself by people who celebrate it or raise my kids in the Netherlands, it will not really affect me. I wonder how other people, who don't live in the Netherlands, feel about this holiday?