Since if one has to cheat in they must have not been in love with that other person. As well as without trust theres no love. In my eyes cheating is definetly wrong but people will do as they please even though they are hurting someone else. Sometimes, but it's always a risk. There's a slight difference between the perception of men cheating vs. women cheating.
Men are more able to separate sex and love, at least that's what they sometimes say.
However, if their GF cheats and she says the same thing, it was just sex, he doesn't believe it. Also, so people collect sexual partners like stamps, and continue this after they're in a relationship. Sometimes they're just addicted to sex, or at least the conquest. It important to talk with your lover or partner as honestly as possible to make sure the two of you are on the same page and have the same understanding of your rules. Of course first off is to ask him what he likes, rough, soft, teasing, wet, all that stuff.