They were arrested for protesting in a place and time there was a ban on protesting. It doesn't matter if they were protesting Zwarte Piet, racism or to save puppies Cruella de Ville: they were arrested for breaking the law. Just like you are doing now, they are playing the victim to turn this whole thing into a "look at the evil racist white devil" story, but on Wikipedia we are supposed to stick to the facts.
FACT is that in the Netherlands there are limits to when and where people are allowed to protest. This goes for neo Nazi's as much as for Zwarte Piet protesters. No source has been provided to support the claim that the reason for the arrest was anything other than breaking the protesting law.
FACT is that a Wikipedia editor claiming "Police reports a BS" needs some good evidence. Founding an entry in an article on a baseless accusation like that, we might as well turn the 9/11 page into the truth as claimed by the conspirators.
FACT is that none of the sources quoted support the claim based on first-hand reports.
So please stop running around in circles rehashing the same non-facts, and either provide a source that actually supports the facts that you are claiming, or admit that there is no factual basis for the claim you want to support that they were arrested for supporting Zwarte Piet.