Talk about twisting the truth (no offense)! Angelo was not possesive and jealous in the beginning. He only became that when Belle's behaviour and attitude towards him changed. She was being snappy, b*tchy and demanding, while being overly friendly with Aden. Of course Angelo would suspect that there was something going on between them behind his back, but with no proof, he decided just to be extra observant around them. The longer time it went, the more sure he became that they were having an affair behind his back. But he still had no proof. And when it first started, they weren't having an affair, but Belle was starting to doubt her relationship with Angelo. Then he got proof in the worst possible way. He walked in on them kissing, and probably also assumed that it had been going on for a while. But, instead of running in and yelling at them and acting like an idiot, he leaves. He has that much self-control. And when the town-meeting started, it was clear that Angelo wasn't going to say anything there. But then of course, Aden had to open that big mouth of his. He basically called Angelo an idiot. Now, who is expecting Angelo just to stay calm now? Aden is rubbing it in when the wound is still fresh, so Angelo responds. Maybe not the most clever thing to do, which it seems like he gets, considering he leaves instead of continuing to humiliate Aden. Then Aden continues to be an idiot and runs after him. Very bad idea. Angelo is hurt and then Aden comes after him, demanding him to apologize? Aden can be very glad that Angelo has enough self-control not to beat the crap out of him. The worst part is that everyone, except Charlie, was on Adelle's side. I can't remember anyone telling them that they'd been acting like a pair of idiots.
But it doesn't end there. Belle and Aden are still rubbing his nose in it, and he makes it crystal clear that he isn't going to let this one go. But he's not 100 % bad (or 100 % good, which is why he doesn't let them be), so he doesn't physically hurt either one of them, just emotionally. But I think he felt that he was hurting the wrong person (I think, I don't know). I think he was angry with Aden, but merely disappointed with Belle. Until she wished that she never had laid eyes on him. I think that's when he went from being angry with just Aden to being angry with the both of them. Now, this is only the way I see it, I don't know if it's the way the writers intended us to see it.
Just to point out with this comment, I think it was shown numerous times that Irene had grave reservations about the Adelle relationship. Even Belle's reluctance to reveal the relationship to Irene was stressed quite a lot. Also to a lesser extent, Geoff and Annie's initial non-acceptance was demonstrated also.
Just to reply to this, Irene might not have been their biggest fan, but it was simply because she was afraid that Belle was going to get hurt. I don't recall her trying to get between them. She let them deal with their own relationship, allowing Belle to make her own decisions. If she was so against the relationship, she wouldn't have let Belle be with him in the first place, and she definitely wouldn't have been so calm when she found out that Belle had cheated on Angelo with Aden. At least that's the way I see it