Capability is not controlled by age, gender or any other damn thing the media wants to use to pump up emotions. Next there will be someone saying that there is no way a midget could cut you with a knife, too short; that female can't shoot you with that gun, small hands; that white person won't hit you with the baseball bat, terrible at sports; that hispanic person won't run you down with that car, can't drive. That's the quality of the argument "too old" to do any harm. Capability does not equate with any of those things. If you want to try your hand at disarming and knife wielder and see how badly you fair get a buddy to use a marks-a-lot as a knife and see what you'd look like at the end. Then imagine all those black spots and lines are stab wounds and areas of your body that have been flayed open then think about what you would do differently.
As to the UK example posted, a knife wielding chav with no will to use the knife is something a bit different than a crazy guy with a knife and no inhibitions. Or it just points out how dangerous old dudes are
Is more training needed for LEOs, yup. No one wants their taxes raised for it though. That said this is not a training issue even though its an easy shot to take at the incident. No amount of hand to hand training will change the fact that you DO NOT go hand to hand with someone who has a knife unless you have some sort of death wish.
