Lest anyone forget, that in order to keep the tribal conflicts, uprisings and such that can be a problem in any government seeking to dominate over a wide variety of people, you keep the squabbling down by being the nastiest, meanest mo-fo in the valley. You bark, the other dogs shut up.
Assad has done this, Khameni did it, Saddam did it, and others.
Assad has been pretty careful to refrain from direct conflict with the US. Khameni and Saddam were not.