"Men are trash" is really no different than "Men are pigs". For decades women use generalized phrases like this to voice frustration with men in a general way. Frankly, I like the phrase. I could see women saying it over drinks at the local pub. "Trash" is subjective so it works. I would consider it prejudiced or hateful if the phrase was "Men are liars" or "Men are lazy" or "Men are stupid".