It's always a good thing to reduce mass shootings. However...
One must consider what you're giving up. Who's to say that the US won't be facing a threat (either foreign or domestic) in 25-50 years from now that will require the citizens to be armed with somewhat capable weapons in order to overcome that threat?
History tells us that things do change, and that gov'ts do become tyrannical, and that economic collapses do happen, and countries do get invaded...
Personally, I'd rather keep the weapons.
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I honestly don't object to reasonable laws that keep guns out of the hands of those who shouldn't have them--like some of the mentally ill or convicted felons or others who should be on a 'do not sell to' list. In this day and age a universal 'do not sell to' list should not be all that difficult to compile, maintain, and made available to all gun dealers etc.
But does anybody seriously believe it is worse to get shot during a violent act than to be bludgeoned to death with a ball bat, or knifed, or blown up with an explosive, or poisoned, or whatever means somebody would use to commit mayhem? And if you are confronted by somebody determined to commit mayhem, what weapon do you prefer an option to choose to deter him?
But it is noted that in almost every single case of mass murders, they were committed in gun free zones. And if making guns illegal was a guarantee that people wouldn't have them, then making drugs, Prostitution, bootlegging, rape, robbery, and assault illegal would mean those things wouldn't exist.
I just don't see how taking rights away from law abiding citizens makes us safer.