Anyone who pays any attention to language understands that words mean what people receive them to mean, not what their roots imply that they ought to mean. As you pointed answer well, etymological arguments get so tiring.

To add just a little bit to your transphobic argument, which I agree with, let’s look at the case of a person who says they are attracted to cisgender men but not to non-binary men.

Transphobic? Clearly. But it’s also not believable. We don’t intellectually choose who we are attracted to.

Attraction arises from within us, a response to stimulus. Certainly, some of it is socialized, but it’s still unconscious.

So if a person says they are categorically not attracted to non-binary men, I think they are actually saying they’ve made a decision not to act on attraction to non-binary men. Like, they’ll look at a hot guy, feel that frisson of sexual response, and then later, after finding out that hot guy identifies as nonbinary, exclude him intellectually as someone they ought to be attracted to.

Not cool. Definitely transphobic.