Our male ape ancestors used to have to fight each other for the reproductive rights to a female. Chimpanzees for example still behave this way today. Chimpanzee females are not choosie maters - they will mate with whoever wins the fight over the other males.

While human females are choosie maters, our more primal instincts are still laying there underneath. I believe one of the primary reasons sexual aggression in men can be welcomed by some women (as long as the man is chosen) is because they still want to feel like the man could have won the fight, if there was one. Male sexual aggression can also demonstrate to the female that the male has a strong desire for the female, which is important from a survival perspective. The female is always worried the male will leave her to fend for herself and her children that will result from the sexual encounter. The stronger the desire for the female, the less likely the male will leave.