It didn't make much sense to me to have the US military kill people because Assad killed people. Now the goal of launching military force to bring Assad to the negotiating table with the rebels sounds like a significant escalation, even with the restriction of no US troops on the ground. Worse, it is a continuing line of thought that I have heard since Vietnam about the vain hope for a democratic element between bad choices at either end of the spectrum. Through military action we can encourage democratic elements that will (miracle of all miracles) come into line with US values and foreign policy objectives. If you buy that I have a unicorn to sell you.
In the mean time there are two million refugees from Syria that could use significant help. The situation is so bad people are leaving Syria to go to iraq.