As was "negro" - and that's kinda the point; just because a word is "official" doesn't make it not discriminatory, just that the discrimination was backed by the power of institutions.

I don't 100% buy the argument that the two words are equivalent, but I can see how "oh you can't come here you are obese" could feel similarly arbitrary as "oh you can't come here you are black"

That's the way these things have always gone and probably always will. Retarded, imbecile, idiot, these were all effectively clinical terms (or whatever best approximated clinical practice in their eras) - they didn't hold an insulting intention initially. People co-opted the terms to make fun of each other, as we do, and so professionals had to shift the clinical vocabulary so they weren't using commonly hurled insults when discussing patients. And that means new words people can use to make fun of each other, yay! Which of course they did, necessitating another rotation. Pretty hilarious if you ask me.

The most recent example in my own life - my wife is in her mid 30s, and is pregnant - some medical professionals call this a "geriatric pregnancy"! But because some folks are getting offended by that term, they're starting to use "advanced maternal age pregnancy". Bit of a mouthful, I think they'll get to keep that one.

Anyway. Carlin had a great bit on this phenomena, he's the one who pointed it out to me.