Upon discovering the situation, the user physically attacked his friend, causing a nosebleed. He also verbally confronted his now ex-girlfriend. The user is now left questioning the appropriateness of his violent reaction, specifically because his friend did not fight back.

You know that overdone scene in movies where a character walks in on their woman getting railed by their best friend? Yeah that was my weekend.
Still shaking as I type this. I (m36) beat the shit of my “friend” of 10years when I saw what I saw. He didn’t press charges, didn’t even fight back and said later he knows he had it coming.
Obviously I did not touch my now ex-gf (33) but holy shit did I curse her out too.
AITAH for attacking my scumbag buddy? No serious hits other than a nosebleed but the fact he didn’t really fight back is fucking with my head. Like I hit someone who couldn’t defend themselves.
Conclusion
The original poster (OP) is dealing with the severe emotional fallout of discovering infidelity, resulting in an immediate and violent physical response toward the partner’s betrayer. The central conflict lies between the understandable impulse for retaliation following a major betrayal and the ethical concern regarding the physical assault on someone who offered no resistance.
Given the physical attack on an unresisting party, is the OP an asshole for assaulting his friend, even though the friend’s actions were the initial cause of the conflict? Or does the extreme betrayal negate responsibility for the resulting physical aggression?
Here’s how people reacted:
You say you feel bad because he did not fight back, well, same if you hit her?
Understand, you are wrong, you are TA. I am just curious how you seperate the facts.
I walked in on my X and her coworker in our living room going at it. Very obvious that it was a guys place, and he had met me.
I threw them both out. Butt naked in the street. Had a grand time when the police showed up.
Domestic disturbance. Naked people in the street. Me, sitting in front of my TV, eating a burger I had just made.
There were no charges they could file against me. He asked if I would give them their things. I handed him a box. Had the guys car keys her purse, his wallet. Legally these were the only things I had to give back. Told him I would gladly return anything they had receipts for, otherwise it was my word against theirs. As the only person on the lease, they would have to explain, in court, what happened.
Met me now wife about 7 months later. Her first question after seeing my place was, whose clothes are these? Lol told her what happened and she replied, so if I intend to cheat on you, hide some clothes out front?
Couldn’t marry her fast enough.
He said he knew he had it coming so it sounds like he wanted you to do that to him so you could get some sort of “restitution” for him sleeping with your girlfriend for who knows how long…
Problem is that the law doesn’t care. People are legally protected from assault, so unfortunately you’re lucky he didn’t press charges, because he could have.
Sorry this happened to you, but you’re better without both of them.
He isn’t in a hospital so I refuse to say what you did was right, but I wouldn’t never say it was wrong either.
NTA
Some random dude off the street:
“Hey buddy, you know she had a man?”
“Nah…”
“Get the fuck out.”
Never see either of them again.
☺️
What you did is a crime.
Did it change anything?
ESH
NTA
He didn’t fight back because he *earned* every punch!!
As a GF. Well done.