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... you're right.
"You don't need to execute someone to stop this happening again, all you need to do is throw Bush, Cheney, and a few others in jail for a few years."
The niggling detail is that this won't happen in a million billion years.
They've already gotten off. If Graner has any incriminating information, then he'll be pardoned (or otherwise released) and will be well paid for his incarceration.
Then, when the Republicans are in power again, all these people (maybe not Graner himself) will come back, and torture and murder a whole lot of other people.