The Keynesian strategy for economic recovery is to use deficit spending to stimulate consumption. How best to do that? Give money, or incentives, to consumers.
Why would we bail out the auto manufacturers? (Or anyone else, for that matter?) As we just saw (again) with the bailout of banks and AIG, trickle down economics doesn't work. The corporate cronies just pocket our money.
If we want to "save Detroit", meaning mostly the jobs and the supply chain, then we should give people money to buy cars.
Look. Clinton/Gore already gave the American auto industry $1,000,000,000 to develop the next generation of automobile. That worked out real well.
Further, there's a strong case that subsidies harm both the recipients and their competitors. The recipients are kept on life support, repeating the same old mistakes. And giving the basket cases money gives them an unfair advantage over their competitors.
In summary, save Detroit by creating incentives for consumers to buy cars. And if the "Big Three" can't survice, there's plenty of other companies ready to take their place.
(Note: Honda and Toyota, arguably the strongest auto manufacturers, have never received subsidies, unlike their Japanese and South Korean brethren. And I think they're better for it.)