Why do I have to be told, that Bush is like Hitler, the the GOP is built on the Nazi party, or what ever. Apart from an emotional argument, I don;t have any intellectual advancement. As far as I can see, it is a motivational argument. It is supposed to make people listen up and be outraged.

But I am already outraged. Those that forget history are bound to Groundhog Day it? We are not repeating history - history does not repeat, as there are all new players and circumstances, political constallations and alliances.
The human continuum on the other hand, in my opinion, means that we are always working with the same experiences of fear, hate, love, solidarity. That's what stays the same, that's what cannot be altered - that is the human condition. And therefore human behavioural paterns repeat.
A strong fearinducing machine makes people follow blindly its disgusting orders. That description fits Nazi's, Stalinism, and Bush. How do I compare them? I don't - I start from human behaviour and use historical examples, but the starting point is the disregard of the stranger, the pushing of fear, not that they are Nazi or Bushists.
The starting point is a attitude towards the human, that respect it in its diversity and multitude and the deviations and perversions.

Anyhoo. My only point is: Comparison that polarise are motivational, not evolutional, or in other words do not progress an argument as they are stuck in the past and are then easily dismissable, for that.