The "historical justification" Putin gave for the war is basically the same argument as the justification for Hitler annexing territories under the policy of Lebensraum. Annexing territories and classifying people as people of Russian descent, passive Russian descent, the "voluntary Russofied," and the "forcibly Russofied"... that's all basically a copy of: Volksdeutsche (ethnically German), Deutschstammige (German descent), Eingedeutsche (volunitarily Germanised), and Ruckdegeutschte (forcibly Germanised).
We know what happens when you appease expansionist dictators, we've seen this film before.