Odds and Ends
5 10, 7:50pm
"Self-defense seems like a good thing but is it really ?"
Yes. Yes it is. Absolutely and unequivocally.
If someone means to do someone else harm, as the aggressor and credibly a threat to that person's bodily integrity, then shooting them dead right then and there is a morally good thing to do, because you are ending, terminally, an aggressive threat.
You're ignoring intent with your argument and presuming that someone who means to harm or kill someone, unprovoked, has as much value to their life as the person they mean to kill. I say they do not; not during or immediately before the moment of aggression at any rate, when violence is justified to stop them and the only violence you can be sure to be effective at stopping them is terminal.
Give everybody a phaser straight from Star Trek that's capable of magically rendering someone unconscious, 100%, every time, with an acceptably low incidence of fatalities from the resulting fall or triggering cardiac arrest and that might change, but until then? Shooting someone who means to kill someone, whether it's yourself or someone else, is absolutely a good thing.