Children learn so many things from their parents... the beginnings of sexuality are among them. Apparently he has had contradictory views of sexuality... his mother showed how degrading men can be to women... how a weak woman would allow that.... and then the rest of the world (media, school, friends... etc) have shown that a man is suppose to be far more respectful towards women.
I wouldn't be surprised if he's a little afraid that he'll become just as degrading as the men his mother used to entertain, and is trying to be the exact opposite of that. So much so, that he's not taking the time to realize how he naturally is.
With you insisting that he becomes more kinky... all you're doing is reminding him of his mother... and his confusing, hurtful childhood. He's being a "good boy" and that's not good enough for you... and he won't be able to understand why.
Also, I've learned that although guys may like for a woman to occasionally be forward with sex... they also like to 'chase' in regards to sex. They like to initiate... and with a guy who has problems like this... he'll need to initiate sex, just to be certain to himself that this is really what he wants --- that he's not being coerced.
I don't think you'll really be able to help him... he's struggling with trying to understand if it's him that controls his sexuality or if it's his sexuality that controls him. And he blames his mother and upbringing for this confusion -- a blame that can easily be placed on anyone who reminds him of his mother, like a 'pushy' girlfriend.
He'll need therapy... and a ton of motivation...
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen