I argue here, however, that the structure of a fiscal stimulus is crucially important and that the package Congress adopted was far from ideal, regardless of the merits of the Keynesian model. Whether countercyclical fiscal policy is beneficial is a more difficult question, but it is not the critical issue if a stimulus package is properly designed. In fact, the Administration could have created a package that stimulated the economy in the short term while improving economic performance in the long term. This package, moreover, would have been immune
to criticism from Republicans. The stimulus adopted was a missed opportunity of colossal proportions.
That the Administration and Congress chose the particular stimulus adopted suggests that stimulating the economy was not their only objective. Instead, the Administration used the recession and the financial crisis to redistribute resources to favored interest groups (unions, the green lobby, and public education) and to increase the size and scope of government. This redistribution does not make every element of the package indefensible, but even the components with a plausible justification were designed in the least productive and most redistributionist way possible.
This, and the fact that it was "paid for" entirely with borrowed money, is why conservatives were against it--not because of the president's skin color.
Update: further in comes this statement, which explains the difference between American conservatism and liberalism:
Another way to describe the choice between spending and tax cuts is to note that under increased spending, the political process decides how to spend the money, whereas under tax cuts, consumers and firms get to decide how to spend the money. Thus, the crucial difference between the two approaches is not whether one accepts the Keynesian model but whether one believes governments or markets make the best decisions about allocating resources.