You can cheat on someone without laying a finger on someone else. Cheating is all about intent, which is why emotional cheating is often more devastating than a physical affair. Personally, I think I'd be more forgiving of a sexual encounter because that's just sex and sex doesn't always mean anything more than an orgasm. Getting all tangled up with someone emotionally is altogether different. Distancing yourself is altogether different, too. All the little ways people cheat without having sex still add up and easily result in the demise of the relationship.