I know of no liberals who supported the Nazis during World War II. There were some ultra-liberals who were fellow-travelers who supported Stalin. When Stalin allied himself with Hitler in 1939, some of these ultra-liberals marched against American involvement in World War 2. But that evaporated overnight when Hitler attacked Russia in 1941.
If they seemed to be “siding” with the Nazis it was only because Stalin had ordered them to tow the Soviet line during 1939-1941.
Perhaps not, because during WWII, Americans were the Nazis' enemies. But prior to WWII, many liberals admired and supported the Nazis and Hitler, John Kennedy's father, for one. Also, though I don't know his political affiliation, I remember clearly that Charles Lindburgh was an admirer of Hitler.