This is a canard pushed by nationalists and “patriots” who have attached their identity and meaning to their country. They love all the positive myths and illusions about how noble and virtuous their nation is. They love the feeling of pride and being part of some sort of heroic legacy, as if they were heroes themseves—when it’s usually nothing more than pathetic flag waving. Anything that exposes a more sordid and unsavoury side to their country’s history is basically a personal attack, because it’s a literal attack on their ego, their worldview, and the very meaning for their existence which they’ve irrationally adopted. The same sort of nonsensical hysterical reaction is found in nearly every country from the same sort of people. British and English nationalists hate being reminded about the British history of the slave trade or colonial conquest, or any of the numerous awful shit Churchill did. Polish nationalists hate being reminded of the antisemitism and that some Poles collaborated with Nazis to kill Jews. The reactions are always denial or rationalisation. They also think everyone is being made to feel guilty as if everyone were responsible. The reality is is that most normal people just recognise these things as things that happened in history, and they feel no shame for bad things that happened decades or centuries ago—just as no one should be feeling proud for things that happened decades or centuries ago for which they have absolutely nothing to do with.