Jess was an asshole in Kyle’s bedroom, but Dean interfering with something that is between Jess and Rory was a) completely unnecessary, since he didn’t know what the fuck happened before he saw Rory come out crying, he immediately jumped towards fighting Jess without a solid reason, and b) it was never about Rory in the first place. Rory was upset because of Jess, but Dean didn’t even take one minute to make sure she’s ok before jumping to whatever conclusion he needed in order to fight Jess, and even when Rory repeatedly yells at them to stop fighting, Dean continues trying to attack and hurt Jess for no reason other than obviously using Rory’s state as an excuse he has to fight Jess. Meanwhile, while Jess's actions in Kyle's bedroom are inexcusable, they also shouldn't be made out to be more than they were and should be interpreted truthfully. He had no malicious intent. He was immediately regretful, knew he was in the wrong, and intended to apologize. He very clearly felt the walls closing in around him and wanted to escape his own body - it wasn't about not getting sex.