"I don't understand women."
Whenever someone has an issue with an SO, then extrapolates that to all women... that's a red flag to me that this guy has a lot more misogynistic views just outside the frame of view.
It is unfortunately common. Pretty much all of the guys I know IRL complain about their SOs with "Pft. Women, right?" And I'm sitting here like... No? Maybe that's just your SO? Or just your SO when they're with you?