anything you call people will offend some people….
i’m sure some chucklefyck doesn’t want to be called a “people”… actually “you people” is often offensive.
it’s all about context, and being as respectful as is reasonable… for example, “retard” literally means “slow”… you could retard the growth of a plant. mentally retarded was just a term for having severe cognitive disabilities that made you unable to interact normally and made you need care to live… but through a history of people abusing those people, and of course using that as an insult made it offensive and dehumanizing.
with calling people “females”, i think it’s because it’s extremely uncommon except for when people are dehumanizing women… so when someone innocently use the term they can be seen as likely oppressive… due to context.
also, given the transphobia thing, and scientific/anthropology defining female as the biological sex and woman as the associated gender, one might think you’re slipping transphobia into regular conversation…
and of course people like simple heuristics so “guys who call women ‘females’ are likely bad people”, works well enough….