Why does elena get mad at Caroline?

It annoys me so much how everytime Caroline hates on Damon or judged him or says something bad about him, Elena gets mad at her. Like sure it’s not nice when someone says bad things about the guy that you like but Elena knows the guy she dating, she knows he’s bad. She gets mad at Caroline for insulting Damon and not getting on with him but excuse me, he slept with her at the beginning and then tried to kill her and then used her as a ‘human blood bag’ and compelled her to do things for him. Why shouldn’t she hate him? And then Elena gets mad at Caroline for hating him? Like what?