The ethnic and religious composition of Syria is roughly similar to the divisions found in Iraq and Lebanon and no less explosive. It seems that the bloodshed, chaos, and uncertainty of Iraq have led most Syrians to the default position that even a bad regime is preferable to the risks of instability.
The business of Dubai is business.
I do not believe that the UAE knowingly permits terrorists to use its territory. But its desire to make itself the major hub for international trade means that Dubai's maintained an open door policy. We know that even in the most democratic societies, it's hard to close the door to those who would do us harm.