I'd say the "exchanges" they had with Estonia, Latvia, Lithuania, Poland, Finland etc. were quite unequal. Expanding your territory through force is the purest form of imperialism, no matter what color your flag is.

That declaration wasn't worth the paper it was written on, as the USSR immediately turned around and tried to forcefully annex these newly independent states (and when it failed tried again some years later).

Yes Finland joined forces with the nazis after the winter war, but the USSR started the winter war attempting to conquer Finland. To blame them for joining forces with the enemy of their enemy after being invaded and losing territory is just wild.

So the argument is that the USSR was so scared of Poland joining the nazis that they made a deal with the nazis to invade it together and divide it between them? How does that make any sense?

The USSR didn't withdraw their troops from the baltic states until the 90s, a good 45 years after the end of WWII.

The Molotov-Ribbentrop pact was a deal between the USSR and nazi Germany detailing who would get what parts of eastern Europe. The existence of other deals and treaties that you think are worse does not change that reality.

If the USSR had been the staunch defender of the slavic peoples from nazis aggression that you claim they were, they would have entered into a defensive pact with the eastern states, not invaded them.

Talk of freedom and brotherhood means nothing when cooperation is gained at the barrel of a gun.