I wouldn't call it a defense mechanism, maybe it is just who he is. That is how I was and still am and I'm married now. The girls need time to adjust out of the high school maturity level and actually know that people like this are better for them then the ones that constantley lie to their face just to get action.
But it depends which life you prefer, one of bold truth that makes you a better person, or one where everyone tells you your breath is minty fresh when it smells like the ass of a dog. I respect and like people more when they tell me I'm doing something wrong, because I can correct that action. The people that tell me "Good Job" too me face when it is infact shitty, are absolute pussies.
If he needs just to get laid, then he needs to cut it out, but if he actually wants something with meaning other then busting a nut in someone then don't change. My experience is people seem to respect you more when they know they can count on you to tell them when they are in the wrong.