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.
Muggle isn’t considered offensive within the world, it’s just the British term for a non-magical person. Wizard/witch for those with magic, muggle for those without (in America we call them No-Maj, which is fucking awful)
Some of the bad characters will say it in a sneering or mean-spirited way, but they often don’t use it at all and go instead for subtler terms like “those lesser than us” or “the filth” and similar
The only term in the series that’s considered “offensive” is mudblood, which is basically a mixed race slur (it’s a wizard/witch born to one or both muggle parents), and it’s very much addressed as not OK to be said and why it shouldn’t be said and how much it can hurt people (from Rowlings fave character, no less!)
It’s insane to me that the person who wrote that into book 2 went on to be a fucking TERF
It’s “the British term” because Rowling made it up.