Check out the above link, then ask yourself how the ban on masks is compatible with this:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
As long as people wearing masks are peaceable, then what difference does it make what they are wearing? I am not arguing for the right to commit crimes while masked, but it seems to me that the banning of masks allows for the intimidation of protesters above and beyond the law. For the same reason that I believe in not allowing your precinct captain to see your ballot card, I believe that you should be allowed to protest anonymously if you feel you need to. The government already has too much power to destroy it's citizens on a whim; hiding thier identity is one of the few protections protesters have from a little extralegal punishment for thier beliefs.