[Yetanfou]

Well, yes, in the USA this is probably the case. The world is a lot bigger than the USA and encompasses a multitude of countries where protesting is best done anonymously. The 'black block' tactics by the likes of AFA/Antifa are another story, these are people who go out with the intention to harm those who they consider to be their opponents, i.e. the opposite of the term 'peaceful protests' which is bandied around so much. They are the ones I'd like to unmask or at least not have masked by any software made to protect the privacy of real protesters.

On the subject of that protester from one video being a murderer on another, not really. If you only have a single source this problem exists and is unavoidable, so much is clear. When you have multiple sources from different angles it becomes possible to correlate the person seen from the back in source A with the murderer in source B and with that identify that person in source A as the murderer.

[burfog]

In one photo, showing a murder, the murderer is seen from the back. (as happened recently in Portland)

In another photo, he is seen from the front, somewhat peacefully protesting. (his daughter was in the vicinity and held a weapon that he could have used)

If the face had been hidden in the protest photo, then that photo would not be useful for solving the murder.