One evil always wins out, and thereby becomes stronger. Our foreign policy should be to support the lesser of two evils, from the standpoint of our national interests. This is why we supported the Soviets against the Nazis during WWII, and various Third World dictators against their communist insurgencies during the Cold War. In Syria's case, the lesser of two evils happens to be Assad. The media is on the side of the Sunni Arabs, most of whom would like to see nothing more than the wholesale extermination of the non-Muslim world. As far as I'm concerned, any enemy of Sunnis in general, and of Sunni Arabs in particular, is someone we shouldn't obstruct if he is dealing with a problem from that quarter. After all, between 9/11 and the campaigns in Iraq and Afghanistan, Sunnis have killed 10,000 Americans and maimed tens of thousands more.
To summarize the Assad regime is not the lesser to two evils, he is an equal evil to Sunni terrorism, so let them fight each other and let them destroy each others.