For example, the guy with the mean girlfriend who degrades him.

Why not just walk away the first time she pulls that? What do they possibly have to gain by sticking around?

I don't understand it at all. Men in a relationship with a woman who treats them like shit. What's the point? Why even talk to someone who hates you?

They could be working on their career, hobbies, video games, jerk to porn, travel, etc.