I'll have to disagree with your assessment. The reason we have freedom of speech in the United States is to prevent the government from silencing critics. The Founder's most definitely did not have the Nazi. Much of your argument resembles the same one used by critics of gun control, which is essentially that banning guns won't stop criminals from getting guns. I understand the sentiment, but I also think a society needs to draw lines around what it will tolerate and what it won't. Nazism and the Confederacy were harmful mindsets that killed people and tore apart nations. The only way to kill it is by education, but that doesn't mean we should let it fester.