How Men Exert Power & Control

Finding the above picture and reading just how men abuse and control their partners really hit home for me.  I have a friend at work that is such a wonderful, bright spirited woman.  However, as long as we have worked together she has been with a very abusive man.  While he does not regularly hit her, he does a number of the things displayed above.  He routinely puts her down, forces her to talk to him on the phone during her lunch time and times her drive home.  If she is more than a few minutes "late" he gives her a hard time about it and asks what she's been doing.  Forget leaving - he tells her that if she leaves he will not let her see their son (this is more complicated).  She is very unhappy but deals with it.  She tries her hardest not to rock the boat.  I can only imagine how much hell her life is on a daily basis.  She always has a smile on her face at work, even when she is dying inside.  I cannot understand why he would treat his Son's Mother this way.  He obviously has his own issues, and promises he will get better but his good behavior does not last.  Why is it that men have to be this way?  What is it that they feel inside that they have to do these things to show their dominance over their partner?  We are always quick to say that the woman should just leave, but it really isn't that easy.  We try to help our friend and coworker as much as we can, and we hope that one day she will be able to finally leave him for good.