Republican Opposition To Auto Bailout

I’ve been wondering why the Republicans are opposing any bailout of auto companies even as they add American Express to the list of companies getting taxpayer bailouts.
I think they are planning on using the financial crisis as an opportunity to get rid of unions. They are saying that the auto companies will have to get rid of “excessive labor costs” and “legacy costs” before they “deserve” a bailout. “Excessive labor costs” in this use means paying union members a decent wage, and legacy costs means paying the promised health care and pensions of retired auto workers.
P.S. This is why they are insisting the auto companies go into bankruptcy, when they didn’t insist on this of financial firms that they bailed out.