I dislike people tossing it out there as well. Most the time I think people use Nazi/Hitler in their discussion because it is the mutually universal relative knowledge of what happened. If you try to compare someones actions say to events in the war of 1812 I don't expect everyone to have a basic understanding of the characters and events in that event in history. Whereas Nazi Germany is so ingrained in parody, satire, documentaries, references it really isn't running out of things to say its merely going to an extreme comparison or relating to an event in history where you would have to have lived under a rock to not know the basics in that part of history.