Yet the biggest, down-low Soviet appeaser in America, FDR, had an ongoing collaboration with Churchill to enter WWII against Germany.
I don't see a contradiction there. The Soviets were allied with Hitler. This is a fact. Roosevelt was a Lefty and came to power and stayed there with the help of American Lefties, including Communists. Yet he was a politician. As WWII in Europe came to a boil, because of events and the views of the American electorate--which was not Communist--Roosevelt ceased to be an ally of Stalin, his enemy's friend.
No one changes sides quicker than a Leftist, whether he's Stalin or Roosevelt.