A guy I'm talking to as a friend wants to attack another guy for talking bad about him to me, is that jealousy?

They sound like a couple of 12 year olds.

Depends on what bad he was talking about. What were his intentions to talk to all that to you?

Things he shared with you can be correct or can be wrong. If you wanted to confirm if everything he shared with you is correct or not. You could have asked your friend without disclosing the name of that guy. If it's just an assumption that the guy shared with you, then you could have asked more details, why he feels like that.

And why did you shared back all this to him? What was your intentions? I am sure you knew, he was not going to love all that.

He sounds like a keeper; marry him. 😂

Yes that does sound like jealousy and he wants to subtly control you

Sounds like a mess.

Seems insecure to me 🤷🏾‍♂️

That's a serious red flag, time to ghost that so called friend for threatening violence, which most likely proved that other guy true.