Anonymizing photos of the violent ones is therefore likely to support their actions by making accountability less likely. To scrub ethically, limit it to the non-violent protestors. To support non-violence, better to help identify the violent people -- police or civilian -- the opposite of anonymizing them.
On a somewhat related note, I wonder if the thousands of people being recorded committing various crimes in the US right now realize that their faces are almost certainly being compiled in various government and private databases, to be matched via facial recognition for the rest of their lives. Yeah, not necessarily a good thing, but am I wrong?