It makes sense, when nobody else has thus far been able to see Harvey outside of Crichton's head, so the joking that he was the one about to get whacked both makes sense, and is maybe a little out of place.

"Not unless you give me a reason to buddy." He hasn't actually looked straight at Crichton except to say that, mostly staring down the leather-clad figment that had noticed him before his friend did.