Is there still any doubt that both parties are very much at fault here? The kids were repeat offenders, and as such, the parents are to blame. They knew it happened before, they failed at disciplining, educating and/or supervising their kids to make sure it would not happen again. There is no need to get into parenting discussions about how to educate children, that's completely besides the matter. The thing is, whatever they did, however they chose to address the issue, they failed. Let's not pretend knocking someone's door at night for hours on end is anything else than harassment.
Van der Poel on the other hand has, to me at least, crossed a line by entering the room of the girls. This is what i find the most inexcusable. He claims he only grabbed one kid by the arm, if that had happened as he caught her red handed trying to knock his door in the hallway, i could somewhat understand that, but chasing them into and entering their room is a totally different matter. It was their room, their safe place. The equivalent of their home away from home. You don't barge into someone's home like that, regardless of what happened prior.