Brilliant, spoken like someone who has probably, a)  never been in a fight in his life, and, b) no idea what is involved in dealing with a distraught person holding a knife.  Armchair quarterbacks make me laugh!.  Of course you try to de-escalate, but in the end, not I, nor the majority of police officers will attempt to wrestle a knife away from someone who is distraught.

 Several years ago, I dealt with two separate incidents, both men with mental health issues, and both holding really large knives.  In each incident, I made it abundantly clear that if they made any move toward me, I would shoot.  Having established that, I did succeed in calming them and getting them to drop the knife.   Had either one of them decided to take a run at me, I would have shot them, without hesitation.  And, I suggest so would you if confronted with the same situation.  Your claims are made sitting in front of your computer, not in a real life situation.