This argument is fallacious in several ways. Without guns involved, confrontations are won by the physically superior party inflicting overwhelming injury on the loser.
People who think that fists, bats, sticks, or stones don't constitute lethal force watch too much TV, where people take beatings and come out of it with a bloody lip at worst.
The fact that the gun makes lethal force easier works solely in favor of the weaker defender, not the stronger attacker. If both are armed, the field is level.
The gun is the only weapon that's as lethal in the hands of an octogenarian as it is in the hands of a weight lifter.
It simply wouldn't work as well as a force equalizer if it wasn't both lethal and easily employable. (cont)