Comparing your political opponents with Nazis is a very violent form of public discourse that should be reserved for actual perpetrators of mass atrocities. If people actually believe it, then it makes physical violence against your opponents seem acceptable or even desirable ("punch a Nazi"). Basically, when you're saying someone is a Nazi then it means you want to treat them like the Nazis were treated after WW2. This implies at least removing their political rights, and possibly imprisoning and executing them as well.