Would love to read more on this. Naïvely, I shared OP’s view of Islamist parties’ intransigence. (Note to third parties: Islamist != Islamic majority or even Islamic parties, and certainly separate from Arab parties.)

> isn't the point of democracy to allow people to be led by those who represent their principles?

Yes. But nothing says democracies are fundamentally stable. It absolutely follows that intolerant populations can systematically elect intolerant leaders who then cause instability.

One reason I'm skeptical of Arab democracy is that Arab nationalism is weak. In the Arab world, Islam and hatred of Israel seem like the most powerful forces. Much stronger than nationalism. Would countries governed by those forces be stable? Would their policies be desirable from the perspective of the rest of the world?

There are Arab democracies that may prove that Islamists can be pragmatic. Tunisia like you said, Iraq, and possibly the new Syrian government. We'll see. The world is always changing.

I think the broader point is that a democracy is unstable when the electorate just votes for their favourite warlord / cleric, who promptly ends / rigs any further elections.

In the Middle East, there appears to be a pattern of electorates voting for / staging a revolution in favour of Islamists, which either leads to a terrible Islamist regime, or leads to an elite coup, which of course destroys the democracy in the process. Worst case scenario all of this happens at once in different places, and you get a terrible civil war.

Democracy is great, but it requires an electorate that actually wants to sustain and retain a democracy. Those appear to be few and far in between.