I don't subscribe to that ideal specifically, but I do see where they're coming from.

Honestly? All adults are individuals. They're capable of making their own decisions... and I'm not responsible for what another adult does. Period. I can see how a person interested in a casual encounter, who has no commitments of their own, would be unconcerned about being the 'other person'. After all, if its a one night stand (or something of similar low-commitment/involvment), the other persons life is almost none of your business. It's their deal, and they make their own choices about their life. If they want to be unfaithful, that's their deal.

As I said, I don't feel that way, or hold those beliefs. I can understand it though. In the same way I don't hold any religious beliefs and I don't believe in the paranormal... but I can still understand that people with those beliefs look at the world differently than I do. They genuinely feel differently about things than I do. I don't have to have their beliefs to understand that's how they feel. I also don't have to agree with them anymore than they must agree with me.. and I'm so thankful for that.

I've always firmly believed that when you make a commitment, you honor it. If you break a promise, that's your own personal failure, and it's your responsibility to own it. Perhaps its not the most morally upright thing to sleep with someone's SO... but unless it's a rape, that person is the one who made the choice to accept an offer or seek out an encounter. They broke their commitment. The person they cheat with is irrelevant, because if someone is even willing to be unfaithful they've already proven their commitment to be false. The act is just kind of... the aftermath and inevitable result of irresolute commitment.

Cheaters find a way. If the person they wanted to fuck was unwilling to sleep with someone in a relationship, the cheater would just lie and do it anyway. Its how they are; dishonest and selfish. I don't know why someone would want to sleep with a person like that, but people sleep with questionable partners all the time. Personally I don't dig casual sex... I like and value commitment, but I know not everyone feels that way.