Personally, if my girl went to get a massage and the dude flicked the bean, I DON'T CARE!
If she was at a bachelorette and there was a male stripper and she touched his cock, I DON'T CARE.
If she has sex with some dude, I'll care, because that is more of a health issue.
To me cheating is deception, if I asked her abuot the stripper or massage and she lied, I'd be pissed, but as long as it was upfront, who gives a shit. A relationship is built on the emotional connection and trust, what you do physically is just that, PHYSICAL.
If she went to a massage therapist, and during the session, became EMOTIONALLY attached to the dude.. I'd be pissed... physically... nah not really. We've messed around with other girls, and its just because it feels good, nothing more, it stops there.
What's the difference between me eating out another chick with her in the room or with her not in the room? As long as she knows about it, its fine right?