I don't think they ever liked Hitler. They took their talking points from Stalin's Comintern operatives. As long as the Molotov-Ribbentrop Pact was in force, and Nazi Germany was friendly with the Soviets, they were friendly to the Nazis. But that was always a marriage of convenience. They were always Soviet sympathizers first and foremost. Nazi Germany was too sympathetic to private enterprise for American leftists - their ideal was always state ownership of all productive enterprises and Nazi Germany was never going to be compatible with it.
Hitler only tolerated private enterprise to the point where it would help him build his war machine. A lot of Nazi rhetoric was as anti-capitalistic as the Soviet rhetoric was....Once the war was won, there is no question that the Nazis' next target for liquidation was to be the business class.