I do understand your point Rap. I'm sure none of the farmers round here are malevolent or dangerous, and neither are the gun sport folk.
It's just that with an automatic in one's hand, one can kill any number of people if one is so inclined. Or very angry. Or mentally unwell.

A knife is bad enough (and there's an increase in knife crime here in UK) but one can't exactly massacre dozens in one fell swoop.
Also, if an officer/PCSO is carrying a gun, an attacker could wrest it from him and use it.

Here, even tasers are quite restricted, and only certain Police Officers are licensed to use one. They're also obliged to give a very clear warning to the suspect before they fire.