Idiots claim Hitler "allied" with the USSR because of the Molotov-Ribbentrop pact, ignoring that:

1. Hitler openly declared his intention to invade the USSR in Mein Kampf and the Soviet archives show us Soviet leadership was well aware of this. It's absurd to suggest they ever had any sort of mutual trust that could be considered an "alliance" since the Soviets were convinced Germany was planning to invade them. Only a year after the pact which is supposedly an "alliance," the Soviet government declared the Wehrmacht as "the most dangerous threat to the Soviet Union." Soviet spies also repeatedly even reported on potential invasions, with Richard Sorge even reporting the exact date of the invasion. Western media likes to portray this 1939-1941 period as an "alliance" where the Hitler breaking the pact was a "sudden shock" to the Soviets, when in reality, the Soviets were paranoid of being invaded, they all were convinced they were going to be invaded, and historians universally agree they were trying to militarily prepare for an invasion.
2. The Munich Agreement signed by western powers such as France and UK also agreed to partition Czechoslovakia to appease Hitler. Was this an alliance? No, it was appeasement. In hindsight, appeasement was the wrong decision, but as they say, hindsight is 20/20. The Holocaust did not begin until 1941, years after both these agreements, and you can't know if someone will break the agreement until they already broke it. In other words, knowing this was a bad decision required seeing into the future. If Hitler never carried out a Holocaust, and WW2 was completely avoided, then we wouldn't be looking back on history with things like Molotov-Ribbontrop pact and the Munich Agreement so poorly.
3. Appeasement could have been avoided in its entirety if UK and France agreed to have a mutual defense treaty with the USSR to contain Germany. The USSR proposed this to the UK and France, but were ignored (source). If you are a weakened country from war, your powerful neighbor has openly stated they wish to invade you, and no one wants to form a military alliance with you, how do you possibly defend yourself? Through appeasement of course.
4. Appeasement did at least delay WW2. The Soviets were very weak from WW1 and their civil war. They needed time to build up their industry, and this should not be understated. You can see a graph here of how fast they were industrializing. Given how close the war between Germany and the Soviets were, without delaying the war, the Soviets might have lost, meaning that this pact delaying the war is arguably one of the most humanitarian political decisions ever carried out, since it prevented the Holocaust from spreading to all of eastern Europe. To quote Stalin, "What did we gain by concluding the non-aggression pact with Germany? We secured our country peace for a year and a half and the opportunity of preparing our forces to repulse fascist Germany should she risk an attack on our country despite the pact. This was a definite advantage for us and a disadvantage for fascist Germany."
5. Some will say the Molotov-Ribbentrop pact is worse than the Munich Agreement because the partition of Poland also included a joint invasion. But nothing in the agreement actually calls for an invasion. The Soviets could've not entered de facto Polish territory at all and still the agreement would not have been voided. It only called for "spheres of influence," meaning that both powers would not try to stretch any of their political influence beyond certain defined boundaries. So the Soviet entry into Polish de facto territory should be treated as a separate question to the Molotov-Ribbentrop pact itself.
6. Indeed, the Soviets did end up militarily entering de facto Polish territory in response to seeing the Germans invade Poland. But what you aren't told is that much of this territory either belonged to Soviet Russia or Ukraine prior, and that Poland took this territory after embarking on an imperialistic conquest, viewing themselves as the rightful inheritors of the Polish empire that existed some centuries prior, so they tried to expand their borders to take land that was the same as that empire.
7. What cities did the Soviets invade? If you name them, you quickly find none of them are actually part of Poland today. They were only held by Poland for an incredibly brief period of time, after Poland's invasion of Ukraine and Russia, and prior to the Soviets taking the land back, not even 2 decades, about 18 years. The only exception is Bialystok and a few small towns around it, which did go beyond what the Poles originally took, but the Soviets restored this land pretty quickly after the Poles complained. The Soviets had no intent to "conquer" or "occupy" Poland, but just took their land back which rightfully belonged to them in the first place.
8. Take Lviv for example. Lviv was controlled by Ukraine, and the declared capitol of the West Ukrainian People's Republic. Poland invaded and the government retreated into exile, and then held this land for 18 years until Soviet Ukraine with the rest of the Soviet Union took it back. It seems to set a weird precedence to insist a country invading another to restore its empire from centuries ago is justified, but that one country using its military to take back land stolen not even a quarter of a lifetime ago is actually the evil one.
9. Poland was settling large amounts of Poles into the territory it took and oppressing the Ukrainians there, rounding them up and putting them into concentration camps. Naturally, this made Poland take interest in Nazi ideology, and came under heavy influence of Nazi Germany. To quote Boris Shaposhnikov from the time, "Poland is already [drawn] into the orbit of the Fascist bloc while seeking to demonstrate supposed independence of its foreign policy."
10. Soviet entry into Polish occupied territory also provided a pathway for Soviets to begin evacuating Jews from the Holocaust. To quote James Rosenberg, "of some 1,750,000 Jews who succeeded in escaping the Axis since the outbreak of hostilities, about 1,600,000 were evacuated by the Soviet Government from Eastern Poland and subsequently occupied Soviet territory and transported far into the Russian interior."
11. While the Soviets eventually did cross into actually rightfully Polish land, this was only when Germany had already taken it over and attacked the USSR, and Germany was carrying out the Holocaust at this point. Meaning, the Soviets liberating Poland from the Nazis is a good thing, and they should be grateful for it, and owe a debt to the Soviet army.
12. Even some western powers were in agreement that the Soviets were right in the expanding in order to contain Hitler. Churchill, for example, would even admit that the Soviet entry into the Baltics was a positive thing because it could help contain Hitler (source). So it's really a new-age historical revisionism to act like nobody knew Hitler had expansionist tendencies and that the Soviets were not in the right trying to contain it.

To summarize: the Molotov-Ribbentrop pact was one of the most humanitarian political decisions in human history. Soviets were trapped in a corner with no allies willing to help them and knowing German expansionism was coming, which would spread the Holocaust throughout all of Eureasia, and they made the hard decisions necessary to stop it, as well as liberating territory unrightfully occupied by Poland that rightfully belonged to several other republics, notably Ukraine. There are millions of people's lives we can point to who were directly saved by this, but potentially tens of millions, even hundreds of millions, who would've died if the Germans managed to defeat the Soviet Union.