Original question...
My usual answer to the clueless question of "Why do you own a gun?" is "Doesn't everyone?"
They usually say "No" in some form, followed by "I don't" in some form.
To which I ask, "Why not? Are you a felon or mentally defective?"
Essentially I turn the question around and make the owning of firearms the normal position in life. Which, by the way, it is.
I don't go out of my way to be offensive about it, I usually act puzzled that one would not own or even want to own a firearm. It's the difference between being a free man (person) and a serf or dependent.
This whole back and forth is an art form, of course, like all real conversations. Some excuses and responses include:
"My spouse doesn't like guns." Aren't they worth protecting?
"I have small children." Aren't they worth protecting?
"The police provide protection." Not based on 911 response times and the Supreme Court decisions.
"It's against my religion." This is tricky if one is not prepared, but neither Judaism nor Christianity forbid armed self-defense.
"I"m afraid of guns." Guns are steel, plastic and wood; how do you ever get near a car or refrigerator?
"I don't know anything about guns." You can certainly learn the basics. You learned to drive, right?
The list goes on. The good part is, one need make up nothing; the truth will do very nicely.