The evidence for the Keynesian worldview is very mixed. Most economists come down in favor or against it because of their prior ideological beliefs. Krugman is a Keynesian because he wants bigger government. I’m an anti-Keynesian because I want smaller government.
Statements like this tell us rather a lot about those who make them. As statements about why people hold macroeconomic views they are wide of the mark. Of course there is confirmation bias, and ideological bias, but as the term ‘bias’ suggests, it does not mean that evidence has no impact on the views of the majority of academics.
The big/small government idea makes no theoretical sense. Why would wanting a larger state make someone a Keynesian? Many Keynesians, and most New Keynesians, nowadays acknowledge that monetary policy should be used to manage demand when it can. They also know that any fiscal stimulus only works, or at least works best, if it involves temporary increases in government spending. So being a Keynesian is not a very effective way of getting a larger state.
It is also obviously false empirically. ...
Parts of the political right have always had a deep ideological problem with Keynesian analysis. As Colander and Landreth describe, the first US Keynesian textbook was banned. New Classical economists, for all the many positive contributions they brought to macro (in the view of most mainstream Keynesians), also tried to overthrow Keynesian analysis and they failed.
When anti-Keynesians tell you that support or otherwise for Keynesian macroeconomics depends on belief about the size of the state, they are telling something about where their own views come from. When they tell you everyone ignores evidence that conflicts with their views, they are telling you how they treat evidence. And the fact that some on the right take this position tells you why anti-Keynesian views continue to survive despite overwhelming evidence in favor of Keynesian theory.