So you think a cop should be able to disarm someone trained to fight with a knife or they dont have enough training?
What about an unarmed professional fighter? Should a cop be expected to take him into custody by himself?
The rest of your conditions I agree with.
This argument is why you have to give police the benefit of the doubt in regards to combative situations. What if the seemingly normal looking man below was resisting arrest, should a cop have to restrain him without using excessive force?