I saw this same thing back in 1978 in Madison, Wisconsin. Two law enforcement officers stood by, one smiling in amusement, as UW students committed assault and battery against a man preaching the Gospel on Library Mall at the foot of State Street.
Now the criminals aren't jaded UW students but Dearborn Muslims; it's not one or two policemen watching, but a crowd of them; it's being documented; then it's publicized on the web; and no one cares.