If you start shooting teenagers in the streets, you'll give them a real reason to riot. No one is willing to risk their lives over a bag of rice, but once you start shooting people it'll be about more than looting, it'll be about chucking molotovs at cops.And here is where I disagree.
It would be the opposite of effective. More riots would come out of it. If you shoot those rioters, you threaten to turn the entire country into chaos. People don't just sit down when their brothers and sisters are killed in cold blood.
It's one thing if you're rioting with some greater purpose. These rioters, by and large, are not. The majority of them are stupid kids looking to cause trouble - and I'm sorry, but no one is stupid enough to risk their life over a bag of rice.
Would there be outcry? Absolutely. But if it were to be well broadcast beforehand that this would occur, no one has the right to complain.
Last time I checked, petty thieves and arsonists aren't usually publicly executed by firing squad...