Hey, if a guy wants to eff everything under the sun, more power to them. But if you are going to get married and claim to be devoted to your wife and the mother of your children, then play by the rules and resist your urges. You know, it is possible not to ACT on these urges. To pull a cliche, you can't have your cake and eat it too, unless this is a mutual understanding.
But seriously, if you want to go be a man and bang random women all over, be single. Otherwise, it's a betrayal of trust that affects the whole family, not just the spouse. I think that's what gets me most, how this kind of thing can destroy the family structure and seriously impair their children's lives.