Nice notice about that sign. The Netherlands is now trying to allow cities to obligate wearing masks, but the statement on that sign, appears to be in line with the Dutch constitution, and jurists even think that judges may based on that not allow a certain obligation. And some juridical analysts claim that the Dutch constitution is very extremely solid on this point. I never knew that (and I've always been well-informed about law and order in general, so I feel ashamed that I didn't know that), and I was actually amazed by it. It does suddenly put the text on that sign to a different light, and apparently not as odd as it may seem at first.
It is clear that the face mask discussion alone is already a political point in the corona debate, no matter if you support the masks or oppose the them. And if you sometimes seem the heath of the discussion of the face masks alone from both those who believe in them and those who don't.... Even discussions about the wall on the Mexican border weren't that hot, I tell ya!