Consider looking at piece of art and saying "I think this part is badly done". This is a very different statement depending whether it is the author saying it, the author's mentor saying it, unrelated person saying it to their friends, or the same unrelated person writing it on twitter. And it doesn't matter whether it is true - it might not even be possible to say, objectively, whether that part is actually badly done.

Same goes for talking about groups of people. Criticising a movement as a member internally, as a member on twitter and as a member of opposing movement is very different, no matter whether it is true or not. And movements are (usually) voluntary - it matters even more when talking about groups of people by categories they can't chose, like cultures, sexual orientations, skin color, etc.

"grouping people by categories they can't choose" is "x-ism". people are more than their skin color, sexuality, or anything else.

There are truths that are empirical (math, physics, etc), but most controversy that includes “x-ism” is about things that are subjective and don’t bucket neatly into a true/false dichotomy.