It’s just fun to do. Don’t overthink the why. I’m guessing you have the same issues with other forms of shooting like skeet/trap shooting and biathlons, etc… One man’s skeet shooting session is another man’s shooting stuff up and target practicing on their ranch type fun.
One might ask what’s wrong with you, that you seem to think that someone that likes to shoot guns for sport and fun has a mental issue. I like to shoot guns, but it never is sourced from a place of doing violence to other humans.
Yes, I know there are a lot of gun enthusiasts that probably like to fantasize while they’re doing it, that they’re in some sort of war games killing people. Can’t speak to them.
There are a bunch of others that don’t really fantasize about play killing people, but just like to be able to protect themselves should the unlikely situation and event descend upon them. There are a lot of people that just like to be prepared to not to be a victim in life.
There are others, that just find it fun to fire off guns and target practice. I like to shoot bows and arrows and throw rocks at things too. I can’t tell you why, it just is. There is zero aggression in my head or me working out frustrations.
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I grew up in a small town and spent lots of time around loaded guns on farms, deer leases, shooting ranges etc and not once in my entire life did I worry that someone shooting the guns was unstable. That way of thinking is silly and childish. I would trust a regular gun owner and user more than someone that is afraid of guns or thinks that anyone that shoots has an anger problem.