Chemical weapons are a terrible thing. I disagree with the assertion that dead is dead. They are a torturous method of killing innocent civilians. They cause civilians to die a gruesome and slow death. Those that survive are permanently disfigured. With conventional weapons, yes, they leave the person dead, but they tend to be considerably quicker in bringing about that death.
In the modern era of warfare, militaries can effectively protect soldiers against their use. That leaves them as nothing more than a weapon of civilian murder — a weapon that kills slowly and gruesomely. A strong moral argument exists that when such weapons are used, the world has a responsibility to take those actions necessary to prevent their further use and punish the perpetrators. This can include military action.
At the same time, war is war and we should not enter it without serious discussion (the exception being in response to a military attack; think Pearl Harbor and us declaring war on Japan the next day). What happened with the Iraq war represented a severe failure of this process and we cannot afford a repeat of that hear. We need to see the evidence put out there. We need to have the discussion. We need to enter this with our eyes open. Remember, even limited strikes put our men and women in uniform in the line of danger and cost us money in a time when we really don't have the money to spare — especially on another war.
Now let me add another wrinkle to the mix: the rebels themselves. They're a disparate group with competing ideologies and beliefs. The only thing they agree on is the fact that Assad must go. One of the strongest groups is nothing more than al-Qaeda's affiliate. If Assad does go, then we could find ourselves with an al-Qaeda run state in the Middle East and bordering, or close to, several key strategic allies in the region (Egypt, Israel, Jordan and Saudi Arabia). Simply put, as horrible as Assad is, he might well be significantly better than the alternative.
If we do attack Assad, and he comes to believe that we are aiming for regime change and not merely inhibiting his use of chemical weapons, he may decide it is time to use it or lose it. His allies in Hezbollah might come to the same decision as well. That could mean gas and rocket attacks on Israel in an attempt to divert attention from what he has done to his own people and to try and unite the Arab world by making it a fight against Israel. In such circumstances Israel would respond with massive firepower, as pretty much any other nation would do given those conditions. The result? We might now be facing a general Middle East war.
However, it comes back to the fact that Assad used chemical weapons. It was a previously stated red line. It was directed at civilians. The man is a brutal dictator. He has no moral claim on power. The only place he should be is a prison cell, which would be nothing more than a waiting area on his way to hell.
My point is that I don't think there really is a right answer. Every answer has the possibility of disastrous consequences. If we intervene, it could literally blow up in our faces. If we fail to intervene, we signal to Assad that he can continue to gas his own people and kill as many of them as necessary to cling to his power. Those who say there are easy answers — whether it is to bomb Syria or to sit on our hands and do nothing — are lying, naive or both.