US Intervention in Syria: Why?

Apparently, our Nobel Peace Prize-Winning President is seriously considering sending military assets into Syria because...we'll I'm not sure way. On one hand we have a  oppressive tyrant who has committed atrocity after atrocity in the pursuit of keeping the country under his thumb. Not really a guy that we like.

On the other hand, we have a force of rebels led by jihadist elements of Al-Queda who are bent on establishing an Islamic based state. These guys aren't exactly who you want to bring home to mama, either.

So they're killing each other in a civil war of sorts. So far, about 100,000 people have been killed. Most recently, the tyrant has used chemical weapon on the rebels, killing a thousand or so. What to do?

When the US (or any country) is making the decision to intervene and bomb (kill people), there needs to be a solid reason why. Killing people is....a big decision, you know? We should be able to answer one of these two questions before taking military action:

1. The use of force is absolutely morally justified in order to protect ourselves, in that we have to do so because it's directly in our interest not to be a victim of an attack. (Self Defense)

2. The use of force is absolutely morally justified in order to protect another group, in that we would not be able to live with ourselves in being a bystander, while another group is harmed. (Defense of others)

Ideally, there should be a mix of the two. In the case of Syria, it's pretty clear that #1 doesn't apply. We're not being attacked, and we're not in any imminent danger of being attacked. It's a civil war in a country between jihadist elements and a secular dictator. Neither one of these groups likes us, and neither one of these groups is sympathetic. Why should we bomb either side? If we do, what's our goal? Is it to level the playing field? Is it to decapitate the regime? Is it to stop the use of chemical weapons, but allow normal killing to continue? Is there a moral difference between killing someone with chemical weapons and shooting them with an AK-47? Either way you're just as dead.

I know it's not a popular philosophy in foreign policy, but the doctrine of "Meh, shit happens..." shouldn't be overlooked here. I know that comes across as isolationist, but there has to be an event somewhere in the world that falls under the category of "Not our problem".

I think Syria qualifies as such.