Complex sentence: The book contends that young boys are encouraged to associate their masculinity with their ability to be sexually intimate with a woman, and that a woman can control a man by socially empowering herself to be the gate-keeper to his sense of masculinity.
Split into simpler sentences: The book contends that young boys are encouraged to be sexually uninhibited and associate their masculinity with their ability to be sexually intimate with a woman. A woman thus socially empowers herself to be the gate-keeper to a man's sense of masculinity.