"Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist." -- John Maynard Keynes, 1936
Now that quote is ironic!
Because that's all that they know, even though it's obvious they have their doubts! They feel compelled to do something. Hence Obama's stimulus was justified as being targetted, timely and temporary, even though it was hardly timely and the targets were gov't programs, especially unions.