If we pull out, Iran will promptly move in and later turn to oil rich Kuwait, Saudi Arabia, the Arab Emirates, Oman, Qatar and Bahrain. They, along with the nut case and Satan's double, Venezuelan (Hugo) Chavez, will then be in control of most of the oil in the world.

In this letter to the editor Clif Hewlett is speaking out against all the "Bush bashers who want us to get our troops out of Iraq." He thinks that it is a good thing that US troops are in Iraq and he backs up his claim with interviewed soldiers who think that being in Iraq is a good thing. Clif concludes that if the US moves its troops out of Iraq then Iran will move right in, and eventually they will take over surrounding countries and control most of the oil in the world.
This argument is using the slippery slope fallacy. He is basing his entire conclusion on the basis that the Iraqi terrorists will move back into their territory, then take over their neighbors, and then collaborate with other countries to take over the oil industry. This may seem plausible but cannot be proven with facts. Just because US troops move out of Iraq does not mean that Iran will do all that Clif stated. However he does strengthen his argument by stateing that Iran does have the power to do what he claims, if the US pulls out, but this does not affirm that they will do it.
If Clif did had backed up his conclusion with historical fact then it would have made a better argument. Also he should not say what Iran will do, but what they might do. Historical facts cannot be denied and they could lend a lot of strength to his argument. Furthermore he should give some data on the Iranian army to show how they could act upon his scenario.