My recent favorite is anthropology ignoring all evidence of women hunting because it didn’t fit social morals of the researchers. Even finding women buried with shields and weapons and people still making excuses.
That’s a good example. Another is from my country, Australia. The idea that the Aborigines were just nomad hunter gatherers was seriously upset by the discovered fish farming settlements in the north of the country as well as the remains of basic stone buildings. Settler farmers have been destroying the evidence of these artifacts for 150 years because they upset the politics of “peaceful European settlement”.