Means are a reflection of values. If your means are screwed up, so are your values.

What supremacists say does not threaten anyone's public safety or peaceful life until they take action on it, or until people who dislike what they say take violent action upon them for saying it. At the point someone takes illegal action is the proper and legal time to oppose it with force. Until then, it is just talk, and in America that is and should be allowed.