Mark, David answered these points in an earlier post. Very well I might add. I think as a police officer, he is very well aware of what a knife can do. And nothing he said in his answers deserves the label of "play". There is nothing in his training that I would label complacent either. It is a different focus.
Please note that I am differentiating still between David's answers and Chris's answers. Though I suspect David may be where Chris wants to go.
I also suspect we may just disagree on this one. I feel David has answered your points and you do not, and that is fine.
There's always room for disagreement.
And, given some time, my thoughts will change.