"Lastly, the answer is NOT to say we can't allow white supremacists or communists or [fill in group we don't like] to demonstrate because they might cause a violent reaction. That's known as a heckler's veto." Agreed.

We are on dangerous ground when anyone believes that outlawing unpopular speech is the right way to go in America. The number who seem to have forgotten high school civics is appalling. Making speech "forbidden" is not only very obviously unconstitutional, it's stupid. The forbidden becomes more enthralling to the deranged and makes its practitioners pseudo-martyrs and heroes. Ignoring and marginalizing the ideas, while working to change minds and hearts one by one to attempt to heal the sickness that turns these minds to revere evil is what will help such ideas diminish.

Evil in some form will always be with us. We can't allow it to be a spectacle, to attract followers, or to greet it with evil and violence in the name of counterprotest, and claim that's acceptable.