As always, "what Digby said"

Sums it up in two paragraphs:

When a liberal activist group accidentally put a 30 second citizen generated ad featuring a comparison between Bush and Hitler on its web site [ed. Move-On in 2004], the political establishment goes nuts.

Glenn Beck, a highly paid television pundit spends an entire hour comparing audience Hitler, Stalin and Mussolini to Obama and the political establishment acts like it's perfectly normal.