Here's what Dr. Phil says about porn in a committed relationship:

"It is not OK behavior. It is a perverse and ridiculous intrusion into your relationship. It is an insult, it is disloyal and it is cheating.
Consider how it makes your partner feel. If it makes your partner feel ugly, hurt, deceived, lied to or inadequate, then it needs to stop. If it is eroding your relationship, it's gone too far.

Pornography isn't real, it's a fantasy. It's makeup, beauty lenses, hair extensions, camera angles, lighting and silicone! It's also somebody's daughter who has taken a really, really wrong turn. She's demeaning herself, debasing herself, humiliating herself and she's being exploited by people who are funded by you. It is a sick, demented, twisted world. It's not healthy, it's not natural and it's not normal.

Viewing internet pornography or engaging in cybersex is a short step to taking cheating to the next level.

You need to tell your partner that viewing pornography is absolutely, unequivocally unacceptable in your relationship. Draw a line: Your partner needs to choose between the pornography or the relationship."

Is Porn Cheating?