No, that’s wrong. Like Ali Sistani, the vast majority of Iranians are Shiite; being born in Iran hardly poisons his validity now as an Iraqi Shiite powerbroker. Ali Sistani is the only thing standing between the Iraq you see now and outright civil war. If we are successful in instilling any version of democracy in Iraq - not necessarily one “friendly” to the US - then Sistani should get a Nobel Peace prize, imo. He’s literally standing in the breech of lawlessness right now, with only his word as an Islamist, an honorable one, to protect him and the country - and Bush’s political ass heading into November. (however, it’s also true that Ali Sistani has been able to mobilize tens of thousands of supporters at will, to turn them out on the street - a potential militia that does double duty, securing both life insurance for Sistani and political clout with the CPA)
The Shiites under Sistani believe that rejecting British rule in 1920 led directly to the rise of Sunni power, resulting in the eventual dominion of Saddam Hussein (a young Shiite firebrand, al Sadr, has consistently called for jihad against the American occupation; right now, Sistani is winning this internecine political battle with Sadr, due primarily to his integrity as a Shiite Islamist and thus his appeal to the Shiite masses). Ali Sistani, as the leader of the Shiites, believes that Iraq made a mistake in 1920 and he’s trying to keep them from making the same mistake today - kicking the Americans out too soon - and is thus preaching patience with the American occupation.
However, stay tuned. It’s not just you who wants him shot, it may be the Sunnis and the Kurds, too. Not to mention al Sadr, and the Turks as well, who’ve historically dominated the region since the Ottoman empire first rose to prominence. Any increase in Kurdish power in Iraq may lead to Turkish problems with their own Kurds, and they may come to see a civil war as preferable to any Kurdish win in Iraq.
If Chalabi can have his way with Bush, though - after Sistani does all the heavy lifting - then you’ll likely get your way.