Mirror neurons, pornography and voyeurism

Thinking about how mirror neurons work makes thinking about pornography and voyeurism all the more interesting, if not confusing. For any of you not familiar with our mirror neurons and how they function, have a look at a very good short little intro video from Nova Science Now
http://www.pbs.org/wgbh/nova/sciencenow/3204/01.html

Basically, when we watch someone else do something, our brain responds almost as if we are doing what we're watching -- we watch a dancer and our motor neurons fire, we watch someone smile or frown and our brain responds as if we're happy and smiling or frowning and fuming. Watching others is the way we learn how to function and behave in our culture, and, because we feel what others feel when we watch them, mirror neurons are also central to having empathy for others.

The implications of this for watching endless hours of violent films, tv or video games is appalling but not surprising, but what does the discovery of mirror neurons tell us about watching porn? If my memory is working at all in this heat tonight, various quirky studies have shown that straight men are primarily turned on by straight porn, gay men by gay porn, and women, whether straight or lesbian, are turned on by all of it. So, for the sake of confusion, what is going on when a straight man is watching hetero porn, or someone who identifies entirely as a top or a bottom is watching S & M porn. The viewers may consciously identify with the individuals in their own identity category, but it would appear that their brains think the viewers are playing all the roles! This is particularly interesting since so much straight porn intended for straight men shows primarily women's bodies.