You had a scary thing happen to you and a gun might have saved your life, you got a different perspective then a gun owner that just likes to shoot at the range. I know people who "think" they live in guilded cages that don't feel the need to even own a firearm.
Everyone is going to act all Gung Ho, but honestly most of us, even you, will NOT shoot to kill anyone.
What do I mean by that??? A guy breaks into your home, and lets say he has a knife. Your able to get your gun and you shoot him in the COM. He drops the knife, and goes down quickly but he is very much alive, and screaming for mercy. You have effectively stopped this person. Similar example same guy with the knife in your home, sees that your armed and quickly drops his knife and surrenders. Shooting to kill means that regardless of what happens you just keep shooting, until the guy is dead, whether he falls to the ground, surrender, or turns to run away. Are you willing to stand over a man, on the ground, pleading for his life and kill him? No, that is outright murder.
What everyone does is Shoot to STOP, not kill. You can shoot someone coming at you 5 times in the COM with a .357 magnum and he can still be very much alive. You can try to STOP someone by wounding them in the leg with a .22 and that person can still wind up dead. I shot until the guy stops attacking me. That could mean that I kill him, wound him, or he surrenders without a shot being fired, either way I stop shooting when he stops being a threat.
It sound like your really good friends. Knowing your history, he should have changed the subject. Knowing your own history, you should realize that not everyone has walked in your shoes and they should not be forced to believe what you believe in regard to their own personal firearms. He has a point, you should keep your handgun on your person or locked up when your away from it.