One of the many reasons people own firearms is self defense. One should be able to defend oneself against an attack above the level at which the attack is launched. For instance, if someone enters an abode armed you will have to respond in an armed manner if you wish to survive in the vast majority of cases. Luck holds no promise for those wishing to survive, especially if luck is all you bring to bear.
When an assailant is large and the person being assaulted is small very often the only thing standing between death and the victim is their ability to respond one level up. The assailant has the advantage of knowing what he or she plans to do. The would be victim has no such knowledge and is at a disadvantage.
Properly utilizing a firearm in self defense has saved countless lives. Taking the right away from people is abandoning them to injury, psychological trauma and worse.