well someone is leaving nice tidy pallets of bricks at these places far from any construction zones and I'm not prepared to believe that the officers who are out watching public spaces 24/7 are just going to let someone do that right before a protest without some kind of shady motive.
I googled around a bit, and several of the pictures of piles of bricks I've seen are situated on brick pavements. Some are apparently new bricks, intended to repair the road, and others are old, damaged bricks, that had been removed, and haven't been carted away yet. Admittedly, at least one of the pallets appeared to have no construction purpose that I could see
in frame; but I can't jump from that to "it was obviously sanctioned by the police."
If there were no protests occurring, and you were to sweep heavily trafficked areas in dozens of major cities, looking for sites of brick pavement repair, how many would you expect to find?
Come on, you've got real atrocities being recorded on camera. You don't need to repeat the hypothetical ones until you get more conclusive evidence.