Racism and nazi salutes is not violence. America is still a democracy and it's better for extremists to protest so everyone can see what they stand for and to then peacefully explain how foolish it is.
There is never a good reason to aggressively oppose a group while they are protesting as this will definitely lead to violence.
I am all for protesting in opposition to racism etc but do it at another time not to deliberately confront extremists
BTW how quickly do you want Christians to condemn this?
What are you expecting them to do?