Qatar and Saudi Arabia are funding military assaults against Assad, and have been for some time. As in Afghanistan, this may have been very early on, early enough to be plausible as a major cause of the violence.
In any event, attacking the people of Syria is not liberating them. Murdering Assad is not liberating them. The proposition that "we" should go around bombing countries whose rulers we dutifully hate whenever the media demonize them is bigoted in the extreme. Imagine that Syria was a white Christian country, like Georgia in the Caucasus. Then when the dictatorial leader starts shelling towns people don't get upset.
Trying to move beyond mindless hate, there is the question of what kind of people are fighting the Damascus regime. The Frankfurter Allgemeine Zeitung recently demonstrated what common sense suggested, namely, it was the Sunni rebels who carried out the recent massacre in Houla intended to justify another violent assault on a Muslim country. (It was common sense because it was the rebels who had their story ready, whereas if the government had carried out the massacre, they would have had their version ready.)
Supporting mass murderers is in no wise a humanitarian act. Instead of being rooted in compassion it is rooted in Christian bigotry against Muslims. The US should withdraw its naval base from Qatar, break relations with the abominable Saudi monarchy and keep its bloody hands off.
