@tacotiiger:
Warning: I haven't been introduced to this particular notion of political correctness before, so you're getting my reaction at first blush and it's possible I'm missing something. Which is not to say I haven't thought it through before posting, for better or for worse.
I respectfully disagree with that grammatical analysis. "Blond-haired" doesn't mean someone who did "the action of blonde hair", or even someone who dyed their hair blond.
Or rather, I can see the argument—that "transgendered" is an odd grammatical construction because it implies "transgender" is either a noun or a verb, when it's neither. But that's a misconstruction: The noun here isn't "transgender" but just "gender" (even if the hyphen is no longer linguistically present, as it is in "blond-haired"; "trans" here is thereby also implied to be an adjective, as it is, not a verb).
Furthermore, a lot of the obvious cultural analogues to me are also "noun-ed"s (e.g. the once-upon-a-time politically-correct "coloured" for people of colour). I can see that there's a counterpoint in "disabled", but the precedent certainly isn't that these are all "verb-ed" adjectives.
But, furthermore, going back to "blonde" and "blonde-haired": To the extent that they're not just interchangeable (and in practice I would usually use them interchangeably without much thought), the former subtly implies to me moreso that the adjective is a defining characteristic of the person in question. All other things held equal, I tend to lean away from defining people by their characteristics where possible; a "blonde-haired" person instead of a "blonde" person, "Jewish people" instead of "Jews". I'm not saying it matters a huge amount, especially in the more subtle cases, just that that is a reason I tend to lean a bit in the more-indirect direction with adjectives. The logic being roughly: A transgender person is not defined by the fact that they are transgender.
I suppose I also believe that anyone who is inclined to think nasty thoughts about a particular group of people is not going to be persuaded by the finer details of language anyway. If anything, it's at most useful as a sort of poker-tell on who is or isn't bigoted. But in this case, I also find the posited grammatical underpinning of the argument to be fundamentally wrong.
Edit: As a side note, while we're talking about grammar, I think "transgender person" also feels a bit tortured to me as an adjective; like having "blondhair person" become a thing. The un-"noun-ed" version should normally be just "trans". But, to be clear, I'm not actually saying transgender is in any way a bad or incorrect word on those grounds, just explaining a possible aspect of my personal aversion; English has boatloads of other nominally-misconstructed words and so the real-world usage speaks for itself for linguistic legitimacy.