INTJ Male 1w9 here. I wouldn't consider than an attack to my integrity. A beautiful, attractive female shows up in my life, and my girlfriend is concerned about the situation and confronts me about it. Is there anything wrong with confrontation? I personally prefer direct, blunt questions "Are you screwing around with that attractive girl" rather than play games.
2 years or 10 years, people can cheat and you're not wrong for being suspicious. If I truly loved my significant other, I would have reassured her nicely and warmly and definitely wouldn't consider an attack to my integrity blah blah. I suppose you attacked his ego, not his integrity, that is why he is upset. His ego is hurt boo hoo.
Anyway, were you out of line? According to me, NO.
How to resolve the situation? You have to talk him out. Tell him your reasons why you felt he was cheating and make him understand. Don't beat around the bush and be straight forward.
The only thing you can do is have a long chat. This incident can either make your relationship deep and more trustworthy, or break it. Talk it out like adults, calmly.
Again, I don't find it an attack. You were concerned and it's understandable. Don't blame yourself or beat yourself up.