The liberals only opposed fascism once it was clear that the Nazis were going to attack them as well. Fascists like Batista in Cuba were worked with to the very end, never once opposing them. As for the soviets, they never did collaborate with the Nazis.

What happened was the soviets spent an entire decade trying to form an anti-Nazi alliance, while the liberals were gleefully working with the Nazis. The soviets signed a non-aggression pact on the eve of war to buy time.