In this particular case, completely ignoring the American invasion et al and thinking only about what Saddam is known to have perpetrated against Iraqis, in my opinion it's thoroughly justified.
I would not be at all dismayed if every head-of-state who either directly ordered (as in the case of Saddam, Pol Pot, and others) or sat on his arse and by way of his edicts allowed (as in the case of Kim Jong-Il, the Grand Wazoos of Sudan, and others) the barbaric suffering of the people they govern, were dragged into the proverbial street and shot. Were I Omnipotent Ruler of All, I would start with the proponents of Sharia law.