Your not wrong, I would say a lot if not most don't kill the owners. But death was just the worst case out come. What about those people that get raped, beaten with bats, or those that get paralyzed because they wouldn't just sit there and watch their daughter or wife get raped.
A gun has the potential to allow you to stop this. Its no guarantee and just because you have a gun does not mean you know how to use it or will have the chance.
A gun is just another tool can give you an advantage over or equalize the situation.
The problem lies with people not respecting guns, teaching their kids to respect guns, and not practicing with them. Someone who has never had a gun and doesn't practice with is probably less safe than without a gun.
The opposite: I was raised in the country, 5 generations of owning guns. I have had access to guns since I was probably 7 or 8. Everyone in my family has for 5 generations. Their has not been one accidental discharge that I know of let alone someone actually getting hurt because of it. The important factor? I was taught long before I had access that guns kill, never point it at something you don't want to die, and always check for a bullet in the barrel (I triple check). So I respect guns for what they are, a tool to use in the correct situation.
This is just one pro gun reason there are other but I really don't want to type any more. There are of course plenty of arguments against guns too. I think it basically boils down to education and a lack of respect for guns that cause a lot of our problems.