Having an Affair while in a serious relationship

Recently, while grieving the passing of my brother, a friend of mine came and seek my advice. yeah like, I don't my own problem to settle. His BF, well ...ex-bf asked for a separation and my friend was not able accept the separation and seek my advice on it. The conversation was: Me: was there a 3rd person? Him: No and not sure. Me: Were you involve in any person including ONS/affair and was caught? Him: yes, but it was a one time. Me: Why you were involved and was he worth of the trouble? Him: (silent) well, He is good looking... and I felt lonely.. My BF was not paying attention to me... Me: So do you think this is the reason? Him: I think so, because when he found out, he said it had changed the whole situation. Me: and that is why your BF prefers to have a 3some? Him: yes... Me: Did he said the breakup was that? Him: he did mentioned that the affair was among other Owhh well, unfortunately I came to know his BF ... well ex-bf, were already looking "casual fun" way before my friend was caught having an affair. So, your BF was caught and you weren't. Does that made any difference? no, both of you are the same. the only difference was that your affair with others was physical and between you is love... unless love no longer exist, then it is physical... so for you to mentioned affair as the reason, while you are committing it also... then Fuck.. you are lower that my friend... unless my friend is not revealing all...