What were those economic policies? He suspended the gold standard, embarked on huge public works programs like Autobahns, protected industry from foreign competition, expanded credit, instituted jobs programs, bullied the private sector on prices and production decisions, vastly expanded the military, enforced capital controls, instituted family planning, penalized smoking, brought about national health care and unemployment insurance, imposed education standards, and eventually ran huge deficits. The Nazi interventionist program was essential to the regime's rejection of the market economy and its embrace of socialism in one country.
Such programs remain widely praised today, even given their failures. They are features of every "capitalist" democracy. Keynes himself admired the Nazi economic program, writing in the foreword to the German edition to the General Theory: "[T]he theory of output as a whole, which is what the following book purports to provide, is much more easily adapted to the conditions of a totalitarian state, than is the theory of production and distribution of a given output produced under the conditions of free competition and a large measure of laissez-faire."
Can't we separate Hitler's Keynesian economics from his murderous policies? In principle, yes. But Rockwell makes the point that a government powerful enough to control this many aspects of the economy will be powerful enough to do some of those other nasty things. Also, as Friedrich Hayek pointed out in The Road to Serfdom, when governments acquire totalitarian power, the worst tend to get on top.