How police respond to you is very dependent on a lot of factors, including your age, race, what you are wearing, where you are, and what time it is. I don’t think you should use your own personal experience as a universal template.
> And why would someone threatening people with a knife deserve benefit of the doubt?
Because, as a society, we should do everything we can to prevent harm to everyone, even people who are acting erratically. There could be all sorts of reasons for the behavior. Anyone can have a psychotic episode, and that shouldn’t immediately earn a death sentence. Of course, I understand that even an innocent person having a psychotic episode can be very dangerous, and I don’t think they should be allowed to hurt others, and it may be necessary to use force, and potentially deadly force, to protect other people.
However, I think that is very different than saying “we shouldn’t worry about the perpetrators well being at all”, or that it is preferable to kill the person rather than take ANY risk that they could hurt someone. The answer lies somewhere in between.