I don't think Hillary Clinton was calling Putin--himself--Adolf Hitler; she was simply stating that his tactics are similar. We can already see that what she said is true. The Crimean parliament has voted to secede from Ukraine and join Russia. It will put the matter before the people of Crimea in the next ten days.
Secretary Clinton also used an interesting phrase in her speech, in which she stated that President Putin did not simply want to solidify Russia, but he wants something more grand. He is looking to "re-Sovietize" the Russian frontier. Perhaps after bringing Ukraine to heel, he will work on the other former Soviet states. Who's next? Georgia? Armenia? Certainly, they contain Russian minority groups worthy of Mother Russia's very firm protection.