Damon/Elena
Not everything is about you and Stefan! I'm just reconciling with Katherine after months of estrangement too, I refuse to feel bad for trying to make sure we stay in a good place. Her good moods are few and far between and I wanted to draw this one out for as long as long as possible.
No, I didn't think you and I would have fun if I invited Katherine. I thought Katherine and I would have fun, and we could be together some other time. I admit, at first I invited Katherine because it would piss people off, but now I just really want to have a nice time with my family. I've been neglecting them because I've been with you and I need to get back in touch with them.
It wasn't just last night, Damon! You're always attacking her and I'm sick of it. Just because you could have said worse doesn't magically make the things you did say okay. Are you seriously trying to make me apologize for defending my sister when literally everyone we know was ganging up on her?