IMHO “males” is also dehumanising, but I digress. When used in the derogatory sense “females” is often beside “men,” implying that women are inferior to men. It’s become somewhat of a “dog-whistle,” which is a form of coded language that the speaker uses to imply a different message to a specific audience (usually some sort of bigotry) while maintaining plausable deniability. Someone may purposely use “females” to refer to women to indicate their own misogyny to people who share their beliefs, and it is intentially ambiguous to prevent women who pick up on it from calling it out. Tmk “males” isn’t commonly loaded in the same way