The most famous forms of Holocaust denial and revisionism tend to focus on Jews, casting doubt, for example, on how many were exterminated in the camps. But denying the impact the Nazis had on the other groups they targeted, including queer and trans people, disabled people and Romani people, is still Holocaust denial. Maybe someone should tell J.K. Rowling.
On your link there, I’m sorry to say the author is making a very silly argument. It boils down to ‘if you see a specific race in this racist caricature then you’re the real racist’. This would only be true if racist caricatures were a new thing never seen before. It’s akin to saying ‘oh i didn’t mean black people when i screamed the n- word. You’re the racist for thinking the n- word refers to black people’.
That’s an extreme example but you see my point that there’s a history that’s being ignored.