I'm sorry, but somebody like Richard Spencer doesn't deserve my polite attention when they want black genocide. You've crossed the line there, and at that point your "free speech" doesn't matter when your kind of politics is killing entire groups of society. Those people should be opposed in any way possible and a punch to the face is perfectly fine with me.
If his rhetoric is inciting violence or encouraging people to rise up and murder black people then you have a pretty good case for legal action on a hate speech charge. However, you live in America, not North Korea, and you still aren't allowed to sucker punch someone on the street because they said something in an interview that offended you you loving facist
This is like, a big part of growing up and being a mature adult.