Your friends didn't like Jason. They thought he was just another fuck boy, who wanted to get into your pants. You kept reassuring them he wasn't. He was a good guy, he just had a rough past. You thought maybe if they met him their options would change.
That didn't work. He tends to be charming and sarcastic, which didn't help his case. But when they started insulting him, that's when you really defended him.
"Would you all SHUT UP!! All he's trying to do is win you guys over! He know what you think of him, and he know you're important to me. So, if you cared about about me sit down, shut up and let him talk! Because that would be amazing!"