I get the sentiment about ANTIFA in particular, however, there's a disturbing trend on the "right" specifically that says something along the lines of "if you're not doing anything wrong, then why hide your face?"
This mindset seems to be very ignorant of abuses under the Obama regime wherein the government targeted "conservatives" for their political views (IRS scandal, anyone?) and similar was alleged about the TEA party movement and facial recognition software at peaceful protests.
With the advent of even better technology, this problem will only worsen. I'm not against PEACEFUL protestors wearing masks....though it does open the door to government planted agent provocateurs stirring up violence and trouble at otherwise peaceful protests and offering them anonymity through identity concealment....but let's face it, the average Joe citizen isn't going to have the wherewithal or connections to track these guys anyway...so I'm not sure that's a valid concern.
Just something to consider as our government becomes ever more tyrannical and thirsty for power.