One big reason is to prevent deflation and the potential for descent into a long stagnation, like the one Japanese people are still suffering from long after their nation's economic bubble burst in the 1990s. It's not certain yet; there are arguments on both sides but Street turns a blind eye to this scary downside of allowing the economy to continue to flounder.
His main tactic was to mock a man who supports the use of deficit spending during a recession. He used the ''ad hominem" fallacy — attacking the opponent instead of the idea — against Paul Krugman. Krugman is one of the many economists of all political persuasions who have argued that our recessionary economy needs to be goosed, and that a good way to do that is for the federal government to use its borrowing powers, just as it did to pull us out of the Great Depression.
Street mocked Krugman's Nobel Prize in Economics as being for work that has been superseded by events. If this startling idea takes hold, we will find ourselves having to dismiss Sir Isaac Newton's contributions to physics three centuries ago by noting that his theories of mechanics have been updated by 20th century quantum mechanics theories. (In truth, the Nobel Prize Committee recognized Krugman in 2008 for his groundbreaking work in 1979 to modernize David Ricardo's theory of the early 1800s regarding comparative advantage. Would Street also have us mocking Ricardo?)
Ironically, in the same paragraph in which he mockingly wrote about Krugman having "Nobel credibility" bestowed upon him, Street lost some credibility when he gave a grossly exaggerated figure for the federal stimulus.