Having found yourself in a war...

Regarding Stalingrad, according to your own words, the USSR is to blame for the deaths of civilians because they didn't evacuate them to the rear. As for the fascists, don't forget that their brains were literally washed until they were practically zombies. That's what fascists are – they believe they are the superior race, and the rest are unworthy of living, so killing civilians is normal for them. But even among them, there were people. If you meant the shooting of a steamboat with tanks, keep in mind that it was the steamboat that was being shot at, not the people. No one cares about wasting ammunition on equipment, and sending infantry inside the steamboat would result in the defenders tearing them apart in the narrow corridors, so it's best to shoot at buildings, steamboats, and other structures with large-caliber weapons, and then use machine guns when people emerge from them.

Afghanistan is an independent sovereign state, and the Cold (and even hot) War between other countries is a war, and no troops from any other state have the right to cross its border.

How naive. In any war, everyone only cares about themselves. And Afghanistan, by the way, as well as Vietnam, Korea, etc., were invaded precisely because of their weakness.