I'll reproduce it here and then explain:
If the large volume of cheating and vote rigging, which has set fire to the hays of people’s anger, is expressed as the evidence of fairness, the republican nature of the state will be killed and in practice, the ideology that Islam and Republicanism are incompatible will be proven.Bolding mine. Think about it. If this coup takes place, if the elections are made meaningless, who wins? Not just the anti-democratic forces in Iran, oh no. The neoconservatives who say that Islam is incompatible with democracy win. A BIG part of their argument against Islam and a big weapon in their war against Islam—and, let's make no mistake, a lot of these guys are barely hiding it—is that while a state can be run by Christian or Jewish or Hindu or Buddhist principles, running a state by Islamic principles is impossible. They claim that those states will inevitably slide into dictatorship. By extension, permitting devout Muslims to engage in democracy was a bad idea, especially in western states. To the neocons, Muslims are a threat to democracy itself.
This outcome will make two groups happy: One, those who since the beginning of revolution stood against Imam and called the Islamic state a dictatorship of the elite who want to take people to heaven by force; and the other, those who in defending the human rights, consider religion and Islam against republicanism. Imam’s fantastic art was to neutralize these dichotomies. I had come to focus on Imam’s approach to neutralize the burgeoning magic of these. Now, by confirming the results of election, by limiting the extent of investigation in a manner that the outcome will not be changed, even though in more than 170 branches the number of cast votes was more than 100% of eligible voters of the riding, the heads of the state have accepted the responsibility of what has happened during the election.
(Mark Steyn has built his career on this assumption.)
Iran's elections, dubious as they were, were the single counter-argument. They were an argument that here was an openly Islamic state that was nonetheless an actual Republic, with all that that entails. It isn't perfect, and isn't even good. But it could improve, without being rescued by the secular west and without being turned into an American client state. The foundations were there.
If the Ahmadinejad/Khamenei/Yazdi faction wins, the perception that Muslims are a danger to democracy will grow like a weed in the rest of the world. The tension between Muslims and non-Muslims will only increase. The "clash of civilizations" really will be in danger of taking place.
That's just what they want.