They are well protected under the First Amendment. And according to WWW.KKK.com "[the KKK] do not promote violence-EVER!" I invite you to take a look at some of the legitimate groups the First Amendment protects at this link. http://www.splcenter.org/get-informed/hate-map Just go to the map and click on an area.
And of course there was no violence that day. It's what the principal was trying to prevent! That's the whole point!