That it's not the same situation. Everyone agrees warmongering is bad, but appeasement was mocked not because it led to the annexation of the Czech Republic, but because it didn't actually keep the UK and France out of a war. Hitler always wanted to invade France. This isn't the same situation, because Putin isn't repeatedly saying he wants to invade NATO, which Hitler did do referring to Poland and the USSR. Putin would likely continue to conquest, almost definitely into Georgia if it doesn't fall in line, but there's no reason to believe he would attack NATO