Snipped for focus...
But wait...How would it look if CS said the opposite, as in: "I think she could hit someone or maybe kill them."? He would look SUPER stupid for being with KA. And he just spent the night with her? He'd be thoroughly aware that he'd look SUPER DUPER stupid. Who wants that?
Human psychology...
I'm not sure half the universe wouldn't say the same thing, given a long term relationship that might not be going anywhere, but wasn't violent, and you might want to be very defensive about your girlfriend choices. You might even have sensed something off, but not put your finger on it. But how would you wrap your head around the fact that your 3-year girlfriend seems to have killed someone, and you never had a clue, really, she could do such a thing? You missed a purple elephant in the room?
So, yeah, self protection would be likely for anyone. I think we should cut CS some slack, not for everything he says, but for many things. I think few of us would have any idea what it would be like to wake up in the morning and find you've been sleeping with a killer for 3 years. I know it would make me feel VERY VERY stupid. I'd be in a big hurry to cover my backside with the notion that she wouldn't hurt a fly. Just like CS.