The Department of Justice Crime Victimization Survey reports for every crime a gun is used against another six are used to defend against a crime. If all those were worst case scenario, your one life saved would cost six lives in return. So if you are truly "pro-life" you would support ones ability to defend themselves.
Speaking of wanting to save lives, there are numerous other tools used in killing people and I see no uproar on that. Vehicles cause more deaths than any other instrument but no one is banning them. Why not, because cars are more useful and we need them? We don't need cars, so if you really want to save lives let's ban cars, alcohol, fast food, cigarettes. No? I didn't think so because that would inconvenience us.