Even if the ayatollahs can crush the opposition, they will have a very reduced capacity to inspire Islamic extremism —and so the second link in what President Bush accurately described as an axis of evil will break.
That is wishful thinking. The Soviet Union had no problem supporting communists and other true believers long after few Russians believed in communism any more. And that support causes us problems long after the Soviet Union disappeared.
Jihadi nuts will have no problem taking support from a "non-Islamist" Iran and the Iranians will gladly provide that support.
Perhaps in time, the impact of this brief mass movement may lead to the downfall of the mullah regime, but until then the regime will be our enemy. The defeat of Iran's protesters will not provide us with a victory despite our failure to support the protesters. This is wishful thinking on a grand scale.