Their "sin" is being in an essentially thankless occupation. The libertarians scream at them for being overbearing and indisciminately violent, and everyone else condemns them for for not being tough enough or instantly effective.
They don't deserve criticism for not catching a virtually uncatchable criminal.
Batman's most feared enemy was Two Face, because he was unpredictable. He flipped a coin to make decisions.
They DO deserve criticism for not living up to generations of phony pretense that they are the protectors of society, and can be counted on to catch such criminals. Their sin is not living up to their hype.
You mean they won't protect us? Then how is gun control supposed to work?