The problem is allowing Russia to become a major player in the region, and allowing Ian's military to start stretching its legs now that they are no longer surrounded. (Plus Obama considers any Muslim rebel a close personal friend. Ahem.)
I understand the wise notion of not wanting our troops to get involved in every civil war and stupid skirmish... but there are ancillary consequences to keep in mind.
Obama is simply set on assassinating Assad....just like he did with Khadafi....and we know how that turned out.