It means acting more responsibly and more mature, on balance. It means behaving in a more subdued masculine manner, rather than an overstated or boorish masculine manner. It means acting more respectfully to women and to everyone, in fact. It means lots of things - the ones I mentioned and more.
It basically means they would behave better than they do now.
When men know that they can behave poorly and still enjoy a woman's sexual goodies, there isn't much incentive for them to improve their conduct and manners. While some people consider 'be true to yourself' to be a mandate for life, I personally find the concept disquieting. I prefer 'be better than yourself.' That may just be me, though.
Living in Las Vegas -- the land where normally subdued folks actually believe anything goes -- your opinion is discounted.
You are sentenced to four hours at the piano bar in the New York, New York Casino.