Most people have to reach a sort of comfort level with another person before they about Porn with them. This is easier between friends than with a partner someone is intimate with. There are several reasons for this one being rejection the other knowing you have the ability in your words and actions to hurt the other person.
When a man is in an intimate relationship with a woman it is considered that he has a deeper access to her inner feelings and so there may be more concern and consideration taken then there would be when he talks with his buddies. While the couple may be considered to be very close they aren’t always considered to be peers. Among men talking about porn is like sharing of common bond. It is a guy thing, locker room talk. The subject of sex is less taboo among men because they are all familiar with the pursuit of pussy and it reinforces their own drives and ambitions on the subject. They may or may not actually talk about masturbating to Porn — it is an unspoken assumption. But with a partner you are intimate with you might be more circumspect because you don’t want to let them know a certain person or another woman is attractive to you. That certain attributes, like big porn star boobs turn you on. You may be more reserved in that regard and if that sex video features women that are very different from your lover you may not want to see it so that you are able to preserve the idea that you are only attracted to her even if it is a foregone conclusion that you are not.
Women do not understand that the desire to fuck a porn star doesn’t reflect on how a man feels about his lover. He just wants the porn star too. By knowing this he keeps himself out of the dog house. He simple understands that there are simply certain rituals that may be observed to preserve an idea even though that idea is faulty or nonsensical. It preserves an illusion and that is essentially what people are after in that particular instance.