[Baltar]

This thread seems to be all over the place, but I'll throw in my two cents. First of all, cheating in a relationship is not "immoral". Cheating is breaking a commitment you've made to someone, and a much better word for this is dishonorable. The fact is that nobody gives a damn if you do this except for you and the person you're in the committed relationship with. And if you're an honorable person you'd simply never do this, in spite of any temptation. That's all there is to it. Case closed.

Furthermore, being married or not doesn't mean much in these cases. Marriage is just a formality* between two people that's used to confirm permanent (well, for the length of the marriage at least) commitment to each other. It also doubles as a signal to others that these two people are a couple and aren't open to being courted anymore.

In reality people can have a monogamous relationship without any formality. After all, those people who get married after years of dating become monogamous long before formally being married. One possible way of reducing divorces and cheating in marriages is to force people to have a mandatory period of engagement of like a year where they can move in, live monogamously for a while, and decide if they really want to be married. Of course this isn't practical since it infringes on civil rights, but with the freedom that we have comes responsibility that many people clearly don't want to honor.

*It also has some legal aspects, but for the purpose of this discussion that can be ignored.