It sounds like a taunt, and I suppose it is, but there are taunts born of sheer bravado - and then there are taunts with purpose from people who sound like they well understand the psychology of their enemy. That assumes, of course, that Barack Obama is really an enemy of ISIS. His actions certainly don't suggest that he sees it that way. But to the extent Obama commands the one force most capable of defeating ISIS should it ever receive orders to try, ISIS at least has to make sure Obama feels no particular incentive to do so.