Snopes: No proof Hitler said it.
Origins: This purported quote from Adolf Hitler about the disarming of citizens being essential to “conquering a nation” is frequently cited in discussions about gun control in the United States, but as far as we know no one has ever turned up a source documenting that Hitler literally said this (or something very similar).
Snopes:
http://www.snopes.com/politics/quotes/disarm.asp
Hitler didn’t have to say it... They did it anyway.
Yeah...there's a reliable source.
Der größte Unsinn, den man in den besetzen Ostgebieten machen könnte, sei der, den unterworfenen Völkern Waffen zu geben. Die Geschicte lehre, daß alle Herrenvölker untergegangen seien, nachdem sie den von ihnen unterworfenen Volkern Waffen bewilligt hatten.
[The most foolish mistake we could possibly make would be to permit the conquered Eastern peoples to have arms. History teaches that all conquerors who have allowed their subject races to carry arms have prepared their own downfall by doing so.]
-— Adolf Hitler (1889-1945), April 11, 1942, quoted in Hitlers Tischegesprache Im Fuhrerhauptquartier 1941-1942.
The Snopes you quote is bankrolled by Soros.
Try to find a better “source” next time.