Godwin's Law posits that the longer an Internet discussion goes on, the greater the risk of an analogy to Hitler and the Nazis. It didn't take long with Ukraine*. Thus, conservatives have compared Vladimir Putin's grab for the Crimea to Hitler's occupation of the Sudetenland on the eve of World War II. That makes President Obama a Chamberlain appeaser. Even Hillary Clinton reportedly brought up Hitler.
Putin is not a Hitler. Obama is not a Chamberlain. This is not Munich revisited — oh, how many foreign policy disasters have we made in order to forestall a "second Munich." This is ignorance mixed with bad taste considering how the Russians suffered under Hitler.
The first thing to remember is that only Americans forget history, and history lays heavy on Ukraine.