The problem is incels use female to dehumanize and reduce women. That is where its use is popularized from and i can tell you that 95+% of the time i hear someone use female to describe a woman, outside of a clinical setting or paper, they are an incel. Some people like you may not be aware, or care, that this is how it is typically used but that doesn’t make it any less offensive. That isn’t someone being “paranoid” and starting with thinking things are dehumanizing. It is -literally- how the term was intended to be used in the context you’re using it.

Imagine going up to someone and calling them an derogatory term and then telling them they are just being paranoid for being offended. If you don’t see the problem in that then i hope you can reflect on that and what this says about you.