Chavez is doing what Hitler did in 1933 and 1934, using his democratic election to consolidate power, persecute opponents etc. Try the V-Crisis website for some perspective on this. There will be elections in Venezuela later this year. They will look a lot less free than the previous ones moving in the direction of a one party election which is what happened to elections in Germany in the 1933-34 period. Its a good comparison for Rumsfeld to make. Hitler was a lot more than the Holocaust, although its his most notorious act. There's an old book called "Berlin Diary" by William L. Shirer, not to mention his large book "The Rise and Fall of the Third Reich." Both books give perspective on the tactics and philosophy of Hitler and the Nazis that are replicated all over the world today from Islamofascist countries to the mainstream media in the United States to Hugo Chavez in Venezuela.
By that definition, there are more than a few folks out there "like Hitler". Why is Rumsfeld using it only on Chavez, and not Castro, or Hamas, or any of the others.
It absolutely dilutes the horror of the 3rd Reich. Mein Kampf was published in 1925, well before Hitler's rise. He pretty much laid out his intentions re: the Jews in that book.
The difference in this case is that Chavez has Daniel Ortega, Bolivia, Cuba, Russia/"Former" USSR, and China to back him up.