Of course Stef has legitimate reasons to be upset. Yes, he broke up with his girlfriend and no I don’t blame him for not wanting to hang out with Damon because honestly, as Carina said, I wouldn’t want to hang out with my sister at all if my boyfriend told me he loved her LOL
But that doesn’t excuse Stefan’s trashy attitude towards Damon. Damon backed off of Elena romantically in season 2 after half-heatedly flirting with her before.
But the fact of the matter is that Stefan ditched Elena last season and treated her pretty damn badly and Damon was the one who was there for her when he wasn’t. Stefan had no right to try to come in between them and undermine the amount they have bonded in his absence. Damon wasn’t pursuing Elena this season. She chose Stefan and he backed off.
I get why Stefan would not want to hang with Damon, I get it. I just hate his fucking “holier than thou O bad, horrible brother of mine” attitude. He has no right to treat his brother like that.