Bush is known to be proud of the number of people executed in Texas under his governance. He's a strong believer in the death penalty. This war in Iraq is politically analogous to an execution. Saddam Hussein's regime is depicted in criminal violation of UN resolution 1441 and images of decapitation are used to describe objectives of undermining the Iraqi leadership. Those witnessing this metaphorical execution will experience 'shock and awe' of the US Military power. Just as the death penalty is intended to discourage capital crimes, so too this action is intended publicly to discourage Iraqi soldiers from participating in the crimes of their leaders. But clearly there is another agenda of discouraging other "rogue states" from offering terrorists safe haven within their borders, and discouraging any nation from threatening the US in any fashion.
But what threat does the death penalty represent for a suicide bomber, or suicide airline pilot, as the case may be? When life has become such a burden that an explosive death is preferable, the death penalty offers no influence. When the leaders of a rogue state know that they are on death row, will they prefer to go out with a bang or with a whisper?