The only time, in the heat of a political argument, I actually called someone a "Nazi," I immediately apologized. He forgave me. He’s my brother, after all.
It’s not a good idea to call people "Nazis" or, in general, to drag any other Third Reich terminology into contemporary political debates. Putting aside for one moment just how offensive it is, it smacks of bad faith and shows sloppy analysis. If you’re trying to make a solid point, and the best you can do is use the ultimate manifestation of evil in modern history as a base for comparison, you’re probably not on very stable ground.