Cops are not trained to be "reasonable" they are trained to use overwhelming sudden force. This is for their own safety, because most people they deal with in close encounters are also not reasonable people.
Then they are trained wrong. It is imperative that cops--the people who patrol the neighborhoods our children play in, who are the first response to a (usually harmless) mentally ill person violating social norms, who are the recourse of overwhelmed parents with unruly children--it is imperative that cops are approachable, amicable, empathic, and reasonable.
Most cops never have any reason to fire their weapon. Being a police officer is a relatively safe profession. Everyone they have contact with has legal rights.