I think I understand. Making the decision to shoot someone, and then living with the consequences of that choice IS a HUGE responsiblity.
I'd guess that most people contemplating shooitng another human being underestimate the effects- look at how negatively that decision affects the people who've had to do it. Even when it's a job-related incident, like for law enforcement, it's a really, really big deal.
While all of us would agree on the concept of self-defense, the reality is likely to be very ugly, messy, and frightening. And that is after you've gone through the extremely difficult process of deciding whether or not to shoot.
It's not like in the movies.
BTW, just because you're not carrying a gun does NOT mean you're defenseless- far from it. The gun is only one VERY SMALL means of protecting yourself. If your "self-defense" begins and ends with your firearm, you're screwed.