Syria isn't Iraq 2003 -- it's Afghanistan 1980
How the hell did we get into that position?
There are no "good guys" in the Syrian war. The Asad regime is among the most brutal on the planet, with a record of torture and mass murder horrific even by Middle Eastern standards. The rebellion against it, though, is increasingly dominated by Islamists who have been carrying out escalating atrocities against Syria's Christian and Alawite minorities. Syria is a diverse country and its only hope for decent governance would be a non-sectarian state recognizing equal civil and political rights for members of all groups. If anything, the rebels' actions will drive the minorities into the arms of the regime. And, yes, al-Qâ'idah units are now in Syria and fighting as part of the rebellion.
Why would we want to help the rebels win? We already know the likely outcome if they do. We've seen this movie before, and even played a similar role in it.
In 1980 we began a long campaign of intervention against a Russian-backed regime in Afghanistan, on behalf of rebels helped and guided by a nearby Islamist country (Pakistan). The motive was to limit the expansion of Soviet power (I suspect there was also an element of revenge for our defeat in Vietnam). In the course of this campaign we ended up supporting the Islamists who were growing in importance among the anti-regime guerrilla forces. The indirect result was that we facilitated the fall of a state which was at least somewhat secular and pro-modernity, and the take-over of the country by Islamist barbarians. Later, Taliban-ruled Afghanistan played host to al-Qâ'idah as the latter carried out a series of attacks on us, culminating in the September 11 atrocity.
Now we're about to begin a campaign of intervention against a Russian-backed regime in Syria -- it's not going to end with a few airstrikes, not after it becomes clear that those airstrikes have had no real impact on the regime's behavior -- in de facto support of rebels helped and guided by a nearby Islamist country (Saudi Arabia). The motive -- punishing the use of chemical weapons -- is, if anything, less vital to our national interests than curbing Soviet expansion was in 1980. By attacking the regime we will inevitably be facilitating the cause of the largely-Islamist rebels. If we do eventually act decisively enough to help bring down the regime, we'll be facilitating a take-over by Islamists who are likely to be about as friendly to us, and about as good for their hapless subjects, as the Taliban were. We won't need to wait years for the new regime to invite al-Qâ'idah in, though. They're already there.
I'm no supporter of the Asad regime. It's a horror. But this is Syria we're talking about. There aren't any good options and it's not in our power to bring them into existence. We can, however, make the situation a lot worse, for ourselves and likely for the Syrians too. And I'm afraid that's exactly what we're about to do.