I reckon there are more hands we beat that call than hands we lose to.
I think people forget that this is the precise question we should be asking when betting in position on the river. One of the several solid things Bart Hanson used to harp on in his training (granted, his training isn't perfect, but he certainly hammers the fundamentals and that's what most of his listeners/followers need) is that when we're checked to on the river we should ask how often we win if we're called on the river. If it's greater than 50% then we should be betting.
I think SB's tiny stack makes this a bet. The discussion gets (a lot) more interesting if he has $300 behind, but we obviously have no fear of getting check raised and also no fear that he might sniff out a super thin value bet (i.e., if we were to bet $100 into his $300 behind on the river looking to get called by one pair).
Also, the high level analysis that: (1) he's a loose passive fish; and (2) we have KINGS!