When it comes to the example of WWII bringing us out of the Great Depression, that is true but it leads to the myth that government spending is efficient and, as a general principle, will help in an economic crisis. War is quite a different thing from the government running the economy for the various needs of a diverse society. The government (of the US during WWII at least) was indeed efficient at the single goal of winning the war. This does not mean that A) all enormous spending by the government is economically helpful or B) it will be efficient in it's spending on whatever it chooses to direct the funds towards.
As for the New Deal there are two sides to that. You have the post-depression programs which focused on relief and recovery. Those you could argue were needed due to the extraordinary circumstances. But programs like that are wholly different from things like wage and price controls which some (many?) say actually increased the duration and intensity of the depression.
As for the New Deal there are two sides to that. You have the post-depression programs which focused on relief and recovery. Those you could argue were needed due to the extraordinary circumstances. But programs like that are wholly different from things like wage and price controls which some (many?) say actually increased the duration and intensity of the depression.