Your premise is wrong, but if it were then there would be little reason for the police to be armed. In the overwhelming majority of interactions between police and other people firearms are not needed. How often do you think the average police officer fires his weapon at another person? Rarely, if ever.
The overwhelming majority of people in the country obey the law and don't need intimidation by an armed person.
Police defeat actual criminals by their ability to call reinforcements, their ability to gather information, and their ability to detain suspects. Rarely do they need their weapons, and when they do very rarely do they need more than a sidearm.