Because people are desperate to hate. They love to hate, and they'll do anything to be able to do so without repercussions, hence why they are so free with the label Nazi.

This is the result of our country's constant use of the Nazi's as targets to be slaughtered without remorse, we create individuals who are so convinced that they can hurt someone just for the ideas they hold, that they feel they are morally justified in doing so. The "Nazi" doesn't even have to do anything, not even express fascist ideology, all these bozos have to do is label someone a nazi and voila, a human punching bag you don't have to feel any regret about hurting. They don't need to worry about pesky things like human rights, or the first amendment, no, they're too busy fighting nazis, just like Grandpa (expect that Grandpa was fighting the aggressive, conquering army of a nation and not just a bunch of people who yell disgusting opinions in the streets) they can't be bothered to behave like mature adults, they can't do that, so they need to use their fists.

Its absolutely vile.