Usual nonsense about guns and, more importantly Rights. First, every dictator state fascist, communist etc who persecuted their people started with "disarming' the populace. Having arms means that it presents a major hurtle to despots.
Secondly, police are "reactive". They come when they're called. It almost all serious cases police cannot prevent a crime, but only arrest the criminal after. With your weapon, you can actually react in real time and stop the death or crime.There are so many hundreds of examples of unarmed people being slaughtered. Some of the saddest lately ,were , for example, in Scandinavia where a lone gunmen randomly walked around and killed at least 72 people. Worse, not even the police at the scene were "armed".
London, terrorists attacked people and the police, on the beat, were not even armed. They were stopped only by "Swat" who appeared 8 minutes later(post multiple deaths). P.S. in England  only 30% of the police are armed.