system
Given the following post, respond as if you're commenting on Reddit:
human
I believe that it is morally acceptable to have sex with someone while they are in a relationship with someone else. CMV

I believe that it is wrong to cheat when you are the one in the relationship because you made an agreement with your SO to be exclusive and you should respect those boundaries in order for the relationship to work. As an outsider, however, if someone chooses to cheat on their SO with you, you are not to blame. You should be able to do whatever you want. The only time it would be wrong to have sex with someone who is in a relationship is if you are friends with the person they are cheating on. In this case, it would be a betrayal of the friendship.
The SO's in the relationship should hold full responsibility to avoid hurting each other, but if they intend on cheating with others, the others do not play a part in the betrayal. By the same logic, if your SO cheats, you should get angry at them, and not be angry at the person they cheated with for tempting them.
You could argue that by enabling the person to cheat with you, you are playing a part in harming their SO. However, if it is impossible for the SO to find out, then they never end up getting hurt and no harm is done at all.
Yes this sounds a lot like I'm trying to justify being the "other" person in this kind of situation, and that's because I am. I cannot seem to see how this is going to be hurtful to the other person if they never find out, and why it would be my responsibility even if they did. If it wasn't me that the cheater was cheating with, it would be someone else. They are the one with bad intentions.
gpt
Your argument suggests that, because the loyal half of the couple is not a friend, deliberately taking action that violates their trust is justifiable. A logical extension of this reasoning is: it is okay to hurt people, so long as you don't have a personal relationship with them. That's thin, at best.