See, that was why I was wondering. There are times, on shows and in books, where it doesn't strike me as odd (like in Dresden Files, when Murphy calls Harry an idiot) while other times it'll make me hem and haw uncertainly (like when Rodney calls John an idiot).

I grew up in a family that, though we are sarcastic with each other, we've never verbally insulted each other. So, yeah, it's not something I'm used to. Plus I'm an incredibly sensitive person, and have been on the wrong end of insults enough to have a very low tolerance for them. So insulting out of love is something I have a hard time wrapping my brain around. Even when it does work, it still makes me itch a little.