To be fair, when Khrushchev ceded Crimea to Ukraine in 1954, he had no idea the Soviet Union was going to break up. He was just moving Crimea from one part of the USSR to another.
Crimea had been a Russian possession since 1784, when Catherine the Great annexed it. Before that, it had been part of the Ottoman Empire.
And so what? Koenigsberg was a center of German culture and the capital of East Prussia for something like 800 years. In 1945, the Soviets arbitrarily renamed it Kaliningrad and annexed it to Russia - despite the fact that it's not even physically connected to the rest of Russia, has no pre-1945 association with Russia, etc.
Given that, would you support the German Army if it chose to invade Kaliningrad? If yes, you're nuts. If no, what's the difference?