In this recent question, an answer was deleted as "spam or rude or abusive" for citing a contributing factor about why the Nazis hated Jews. In reference to the writings of Adolf Hitler, the user wrote:
Nazis didn't hate Jews because they were jews but because, at the time, they represented the main endorsers of communism and the things that destroyed or betrayed their country.
and in his comments he clarified:
Hitler, in his book puts Communists and Jews on the same page as destroyers and betrayers of Germany, even saying that jews where the ones to push communism to the west.
Following comments he changed this line to try to make his point more clear that this was the influence of Hitler and not an objective fact, but his answer still got deleted.
Nazis didn't hate Jews because they were jews. It's not a question about ethnicity or religion. They hated jews based on their association to communism which was as everyone knows, pressed by the ideologies of Hitler.
While this is obviously a touchy subject, the user was very clear that this was not his personal opinion, nor was he encouraging people to believe in the racist opinions of Adolf Hitler, but he was explaining a historical racist perspective that was relevant in context of the answer he was giving.
To be clear, some people expressed strong opinions that the statement was an oversimplification. They called Adolph Hitler a lier and a psychopath (I think that goes without saying) and that his this view ignores a much longer more complex history of racism in Germany. On that level, I am not against the downvotes that the question received due to lack of completeness and clarity, I am only calling into question the use of moderation to delete it as "spam or rude or abusive". There was clearly no malice or racism meant by the user's post, and it seems he was trying to be responsive to comments to resolve an issue.
In the context of World Building, understanding how racism or any other potentially offensive belief system works in the real world is a very important topic when trying to create a setting where they do exist. Questions and answers should be allowed to discuss topics like racism as long as they are not written in a way designed to actively encourage it.