The parent post is not "making up" rationalizations nor do I see an attempt to justify Soviet repression.
The Soviets were victims... earlier, during World War II, when their territory was razed to the ground and their people targeted for total racial extermination, and also faced the brunt of that war -- the most destructive war ever -- and did most of the blood shedding. That has to leave a permanent mark in the national psyche. A lot of what they did afterwards was making sure nobody and no country was ever in the position to do that to them, again. They definitely were creating buffer zones to protect their homeland, and I believe most modern analyses agree on this.
This doesn't make them saints. Yes, they were repressive and brutal to satellites they believed felt out of line. But it's not "making up rationalizations", it's what actually happened, and it does explain things.
Also,
> Not expansionist at all
Most powers were expansionist in some way or the other during World War II and its immediate aftermath.