Men are naturally more aggressive and larger. We get that from the apes we evolved from. Our height was originally useful to survival because it scares predators. Men generally defended females, children, and the weak by standing tall, acting fierce, and using sticks. Eventually these traits as well, as the impracticality of pregnant or nursing women's involvement, made men the hunters and warriors when we figured out how to do that. The only other major physical difference (besides the obvious ones) is that women have brains that are more efficient for transmitting information between hemispheres.
Aside from that, it's almost all conditioned. It seems natural. Much of it is based on ancient, ancient shapings of culture, some of which were essential to our survival in a different context. But it changes over time and early anthropologists found out in studies of cultures that gender norms are far from universal (though matriarchy is extremely rare and it is questionable how embellished the claims were of a tribe with opposite gender norms- it was during a festival of some sort. But that is because of the practicalities created by men being larger and women going through periods of birthing and nursing, not natural inclination... If societies did have gender roles reversed in the days of hunting and gathering, they probably died out or switched).
Men are more aggressive and possibly more sexually promiscuous (though that's debatable) by nature. But how you are taught to control or express those things is a lot more important. Humans can learn to ignore almost any natural impulse. We are creatures of culture.
And men who treat women bad learn it from somewhere. They use "nature" arguments as an excuse.

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