My $1/50: A group of the people who dehumanize Hitler are those who believe "anything human is good," a general liberal belief. To reconcile that with "mass murder isn't good," Hitler must be inhuman. I side with those in the thread who find demonizing Hitler counterproductive, since new fascists and megalomaniacs are intensely human: recognizing people who exhibit Hitleresque mania is necessary to protecting ourselves from such people.
Yadda yadda blah.
Addendum: See also a review of Benigni's Life is Beautiful mentioned in the thread. I'd actually kind of like to see it, now.