The police should follow the rules laid out for them. If they don't, I would very much like to see them in prison.
a) The rights were preserved, the assaulter walks free on account of the NYPD's misconduct. The rock throwers have zero cause to be upset, the law protected them from the police overreach successfully.
b) The student was not charged with "anti-war sentiment". He was charged with assault, for throwing rocks at people.