Iraq was a full-scale invasion with the intention of occupying the country. It was reasonable to base a position on the likelihood that the US army would not bring democracy but bring one or other kind of terrible mess. It wasn't a question of the immediate slaughter of a revolutionary movement.
Libya might evolve in that direction, in which case I will oppose it.
The fundamental thing right now is that what was happening in Libya was part of an unfolding revolution across the region. Its bloody defeat in Benghazi would have been an immense set-back for the prospects for democracy, not to mention socialism, across the Middle East. Of course what is happening now has its attendant dangers, too. But Gaddafi's victory would have been - would still be - much worse. (I am not making a case for an 'Arab revolution' or 'revolutionary process' before some irritating pedant tries giving me lectures on that score).
This fucking matters, David. What's been happening in the MIddle East is the most important and hopeful thing to have happened in my political lifetime, which is considerably longer than your actual lifetime. Of course it's a terrible tragedy that the Libyan people weren't able to simply to dispatch Gaddafi by themselves. I wish to God they had; and the new situation is for sure a set-back. But it is nothing like as disastrous a set-back as Gaddafi wading triumphantly through Benghazi in blood. That the left can't 'get' this elementary fact seems to me more than anything I have ever seen confirmation of its irrelevance and utter stupidity.
And I think you underestimate normal people's intelligence. Anyone who is not a left-educated twit can see that military intervention in Libya is not automatically the same as any old other military intervention, and will be able to oppose others which are not the same.