It's not "You're not normal" but "I'd be running away from you if I were trying to have a normal life", though... which, when you're not running away or trying to have a normal life, does not mean the same as when you are (context and gestures/intonation make the difference). I bet there are a lot of people who'd be more flattered to think of themselves as people you don't try to have an ordinary life with, than as people one would look for if one was to settle down and lead the 'normal life' with. (I think I'm one of those.) But it's a matter of taste.

I agree it's miscommunication, though, and Spike's reading is easy to see, and it's completely unsurprising that he felt offended.