Heteronomous morality comes from without, imposed on someone or something by the Other. Autonomous morality comes from within. We want to impose Western heteronomy on sovereign/autonomous Syria.
We think chemical weapons are especially reprehensible, but, I hold that if you don't get involved when 100,000 people are slaughtered, why the sudden moral outrage when a few thousand are poisoned with gas? I don't believe that anyone in our government, at the highest levels, cares about the chemical attack in a moral sense. If we would just quit pretending that this is about propriety (given the immoral drone strikes we use every single day that target civilians), and start admitting that we fear chemical attacks on our shores, and we want a reason to destroy the ability to manufacture them, then the insincere hand-wringing about striking Syria would be unnecessary. Or, call it "national interests." But, spare us the performance of moral outrage. I'd much rather someone say, "Using chemical weapons crosses a line into terrorism that we have decided not to let anyone do in this world. If you don't like it, tough. We will come for anyone who uses them, and we will destroy them and their ability to make and use them," rather than all this pussyfooting around about Congressional permission and the evilness of someone using chemical weapons.
Hell, our cops used tear gas on Occupy Wall Street protesters; since I started writing this post, some cop somewhere has peppersprayed some citizen for not expressly following his instructions. Should we start bombing cops for using chemical weapons on the citizenry? No, we shouldn't. Just like we should stay the hell out of Syria. I don't want my boy dying over there, and I don't want anyone else's boy dying over there. Let the Syrians fight each other for control of their own country. I reject anyone who claims that chemical weapons mean that we should respond now, when this has been going on all along: