I don't know who was in the wrong here, maybe the guy have said something he shouldn't, but, nevertheless, McGregor is on a downward spiral and he's not aging gracefully. He needs to sort himself out and find a meaningful way for the rest of his life. Abusing substances and hookers won't take him anywhere.
I dont know the story around that situation on Ibiza, but whenever someone sees a professional fighter, I really dont think that this person will try to say something bad, disrespectful or try to piss off a fighter. That would be just stupidest thing to do, because a pro fighter, even former or a drunk junkie like Conor, can whoops regular persons ass easily
I think that that dude wanted to take a picture with Conor, or say something, but Conor replied to that with aggression. Some fans can be really annoying and persisting, easily breaking personal space, but replying on that with aggression is not the best way to act. I think it was Connor's ego, along with the drinking and the place they were in. As you said, when someone sees a fighter, whether he's an ex-fighter or not, they're not going to try to insult him. So, I think it was Connor being himself.