[Dean blinks at "skinjob" and he would've asked about that, except:] Did I say I wasn't concerned?

I'm concerned about half the people on this ship, but until they do something, there's not a lot to be gained from being worked up about it. David's paired, even, and moreover he's paired with Aya - that means she knows whatever there is to know about him, and there's a better chance that if he's a risk, she'll head it off.

Not the case with... others.