Have you ever had those raids where your fire team just doesn't work to you. Either if they just suck, or one of them dropped the n word. You just start thinking HOW can I leave politely or what can I say that is really random and stupid and will confuse them to make my escape? I've gone between saying I've played too much destiny and my eyes hurt or my hamster just got the news that he's been accepted to university, depending on the group.
EDIT: if you want Leave your best leaving lines, serious or not.
-
I just stop talking, bring up Ghost and hold triangle tell I'm gone. If I'm leaving a raid cause of some asshats I'm damn sure not going to tell them why. They don't deserve to know, and I have no patience for that.