lyssa,
First, I'll add my gratuitous "You look tasty"
Second, I'll give you my 2¢ as a man who's been on the other side of this issue.
"If I were enough for you, you wouldn't need to look at that $#!%". Every man has heard that at least once.
If he's choosing to masturbate to porn INSTEAD of having sex, then there is a problem. Too much fighting gives a guy the impression that she doesn't want to be touched, and makes him gun-shy of approaching her, afraid that she will reject him.
If he's masturbating to porn, and having MORE sex with you, then he's just warming up his engine for you. Like having a glass of wine before dinner to stimulate the appetite for the main course. It's good without the wine, but a gourmet knows that building anticipation for the main course enhances the senses. After facing 90 minutes of traffic, trying to get dinner ready, getting the kids throught their homework, putting away the dishes, folding laundry, getting the kids off to bed, it can be a little hard to feel "in the mood" sometimes. Browsing a little 'eye candy' gets me anxious and eager to be in the mood later, and I definately give her signals all evening.
Third (gee three for the price of two) here's an easy way to assuage your guilt. Buy something from eroscomix.com (XXX Comic books) and when you are going to be gone for a while (visiting mom, late night at work, whatever) leave it for him with a note saying "Hope this keeps your fire burning till I get back". He'll get several messages, even if he is not consciously aware that he did. 1. That you understand that looking at porn gets him worked up and anxious about sex WITH you. 2. That you take a 'classy' approach. A well drawn XXX comic is a work of artistic talent. 3. That you are not threatened by the fantasy protrayed in the art form. Who could think that their man is going to step out on them and hook up with paper and ink lines for a relationship?
OK, time to get off my soapbox and quit rambling.