I'm not dutch, so this whole tradition seems silly to me. But, that said - Blackface isn't inheretly racist, it's racist because of historical cnotation. In countries without this kind of history, blackface doesn't have to racist. For example, if someone did blackface in my country, at worst no one would even know what the fuck he's trying to do, because there's conotation at all of blackface around here. I imagine the situation is about the same for dutch people.
The cop in the video was definitley an asshole though.