Krauthammer on totalitarian discourse

This has become a consistent tactic of the radical left on many issues. Attempting to shut down debate by declaring that an issue is "settled" From abortion and Obamacare (it's the law of the land) to global warming ("settled science") to pretty much any issue of the week that they want to screech about.
The question becomes will we, as a society, allow the radical leftist/communists to control the discourse or push back against the thug tactics being used against us?