We are funding the rebels because it is preferable to us putting American boots on the ground in another Muslim nation. (eta, not to mention $60 mil to aid rebels is a speck of what it would cost to put troops on the ground--costing Billions a day).
Iraq didn't earn us much international goodwill, and I think we have learned our lesson. Sometimes people in the Muslim world would prefer being at the mercy of evil murderous dictators, rather than accept American troops in their nation. That's just the way it is.
I have a laundry list of serious criticisms about President Obama, but I applaud him for taking this more conservative approach to deal with Assad. President Bush's war in Iraq, although I think he was well-intentioned, was a disaster for the Iraqi people, especially Christians (my husband is a Christian from Iraq--his family has really suffered, and the last family members are still trying to get out.)