I say that it depends. If the person they are cheating with is a person that you know and who is aware of the situation then yes, I may confront them. In reality fighting with them is not worth anything. It would not solve one thing. People need to remember that sometimes the person your significant other is cheating with knows that they are in a relationship but sometimes they do not. And it is not ONLY the other persons fault. Your significant other IS guilty also. So many times I see people fighting with the other person involved but yet forgive their BF/GF right away. It does not make sense to me because your partner is the one who is betraying you the most, breaking your trust and their word. If you could work it out that is great, but if the other party was aware that the person they are dating is already attached, your words of confrontation are not really going to matter to them, just going to add fuel to the fire.