Stalin would object and claim it was Japan that started the war, and he signed Molotov-Ribbentrop because the allies were purposefully giving Germany a long leash and appeasing them and Japan so they could go around thrashing people and become a bigger menace to contain the soviets. Japan and Russia were fighting eachother long before poland got invaded. Molotov-Ribbentrop happened AFTER the appeasement of Hitler. Stalin would argue it’s not a way to make friends with Hitler - but a way to fracture the fascist-imperialist-capitalist bloc while giving the glorious Soviet Union a free hand to liberate the workers. It was an enemy of my enemy is my friend situation.

Realistically, no matter what Stalin did, Hitler was always going to go stomping around Europe, Germany was backed into a corner by debt and spending into doing something to expand the economy, and the Nazis were very ideological about these matters practical concerns be damned.