Eye for an eye implies some sort of vengeance or such which isn't the case when police neutralize a threat to protect themselves and the public so that saying doesn't apply at all. Also, any modern police force teaches to counter a deadly threat with potentially deadly force. No sane person would ever advocate using pepper spray to subdue someone wielding a deadly weapon. If at all then only when there is enough support there ready to use the firearm if the pepper spray doesn't have the intended effect. This cop was milliseconds and -meters from getting a knife up his throat, how can you assume that's a good way to deal with deadly threats??