Using female as a noun (rather than as an adjective, such as in the phrase “female firefighter”, or any phrase of the format “female $noun”) is generally overly clinical and dehumanizing. Some people do it out of habit due to their profession-- usually researchers or soldiers-- but they usually say “males and females”, which while still weird isn’t the worst.

The guys who say “men and females” are the ones you need to watch out for.