Sistani aided the American occupation, according to many Arabs and Arab Americans. Sistani did not call for militant jihad, he did not encourage the Iraqi Shia to fight the Americans. The resistance-minded Arabs in general respect Muqtada al Sadr more than Sistani. Watch this short documentary about Sistani to understand why.
Arabs seem to praise only the Iraqis who fight Americans. Sistani does not want to fight the Americans.
I think if anybody can change Chalabi's mind on the Baathist ban, it is Sistani.