This is a situation that happened 2 years ago and I’ve pretty much come to my own conclusion now but I think it would be interesting to hear reddit’s opinion.

I was 17, never had a girlfriend, my mate had just broken up with this girl I barely knew. The break up was one of those “let’s take a break”  things so my friend was still not sure how they stood. 

Three weeks go by and I suddenly get to know her at a couple of parties and things start moving quickly. We were both frustrated with my friend (honestly he had been a bit of a dick at the time but it was pretty minor stuff) and so broke the ice by complaining about him. (We quickly moved on to other topics but I still feel guilty about this) I started dating her a week later because I was so excited to have a girl where there was mutual attraction and we were having fun. 

A week or so later, I told my friend about the relationship and it upset him a lot, saying that I should have spoken to him about it beforehand and “asked for permission.” After this, he started telling everyone at school about the situation and that I had “betrayed and manipulated” him and it turned a lot of people against me. Every time I would try to talk to him and ask him to keep the issue between us, he would become very defensive and at one point said “Fuck you u/McCleavage.” He never swore. Pretty soon after, we were no longer friends.

AITA?

Aftermath; My relationship with this girl ended after 3 months. My friend and I didn’t speak for another 6 months but then we spoke about everything and honestly we’re much better friends now than we’ve ever been so there is a happy ending to this story :) 
I’ll comment my personal AITA judgment for myself after anyone else has already made up their minds, don’t want to bias anyone.