Earlier quoted context omitted.
> immature Get your point across without stomping a category of person.
A category of person? Being immature means you behave immature. Scolding someone for behaviour is very different than scolding them for something they can't change about them selves (e.g. like where they have been born). Usually we also factor in age when calling someone immature. So if someone calls you immature, they mean "immature given your age", so it is certainly different from e.g. hating on all kids, teenager…
Immature: Not fully formed or developed; not grown [1]
It depends on what sense you use it in, just like the r-word.
> Scolding someone for behaviour is very different than scolding them for something they can't change about them selves (e.g. like where they have been born).
Literally what the r-word controversy is about. Glad you finally get it. Except of course if you think that someone was being scolded for having mental deficiency or specifically an IQ below 70 or something, which I doubt and which I would agree would be just as uncouth as scolding an immature person (in the sense of not being fully developed or grown) for being immature as they can't change that about themselves.