[microbet]

If he's doing that because he already has the flush, you are down two outs.

If he's doing it because he has a straight draw and a flush draw, you are behind.

If he's doing it because he has a pair, it is pretty much a coin flip.

If he's doing it with absolutely nothing, he still has outs.

I think this is a situation where in the third or fourth level it might be a call, but here it is a fold. That's partly because with one player (and possibly more since this is often contagious) that plays like this you have a decent chance at being in a similar situation with a good made hand.

However, I think it is close because a plurality of the time he will just have a pair and be trying to protect against the flush, or a Kc and drawing himself.