Oh, that's all quite true, it just has nothing to do with Stalingrad, specifically.
Stalin was a brutal, evil man, who oppressed his people horribly. With the initial German invasion, many soviet citizens, especially minorities, were hopeful that it would mean liberation from Stalin and did embrace the German armies.
Of course, Nazis being Nazis, that wasn't a good idea of them. You can't really say it was Hitler's mistake to kill these minorities, because it was consistent with who he was, and with his entire purpose of invading Eastern Europe in the first place.
And this doesn't have much to do with Stalingrad, because the Stalingrad campaign happened a year after the initial invasion, and by then the Soviet citizens, even many of the non-Russian minorities, had few illusions about what domination by Germany meant for them.
Let's not go too far here. There's always different interpretations and bias.