There's a seriously demented issue in this country of fantasying about the wars and turning it into exactly the opposite sort of event that it should be, particularly I speak of the gatekeepers that think not wearing a piece of plastic merchandise is somehow a morally repugnant act second only to being a literal nazi.
This is nothing more then regrettable, but it's also not surprising considering how blinded a great swath of this country is to British history (or any history), people are only in tune with the idea of what the war represented, not the facts and so you get this. It could easily be that the ignoramuses that did this (assuming it wasn't just a dog or a gust of wind) are/will be ironically these very same war worshipers.
I don't think it's unbelievable in the slightest that this can occur, this is what a lack of actual education on all facets of history looks like. Only seeing the positive parts of history makes for an incompetent mind and after many decades of rot culminating in an almost mythological lore, it's inevitable that people stop caring and that it becomes a point of polarisation for some or apathy for many... Maybe it's unavoidable, but I feel reliable education since the end of the war might have provided some sanity, certainly hopeless now though.