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

Subtle changes in diction can sometimes dramatically impact how your message is interpreted. Language evolves, and words can take on additional (perfecly valid) meaning over time that are only added to a dictionary after being well-established. This can cause misunderstandings, as demonstrated in this thread. I’m sure you have no negative intentions, but to many it does not seem that way. The takeaway is that a small change in phrasing or words can decide how effectively your meaning is communicated, even if you are unaware of it. Language is messy, and consists of mutual understandings of what a given “word” means. In this case, the hidden negative connotation in “females” is causing you to be misunderstood. I believe using “woman” instead would reflect what you meant without causing anybody to be uncomfortable. Best regards