Never thought of it that way, but you're right cuban... Insightful.
When an armed man and an unarmed man get involved in fisticuffs, you can pretty much assume the unarmed man started it. There are a lot of reasons for this.
I might modify that to "when an armed man, and especially one who is legally armed..."
Legally armed people tend to be very law-abiding. They don't generally go around starting fistfights.
Armed men who are about to get into a fistfight also don't call the police first.
Armed men don't generally start a fistfight, because they know it could end with them having to use their gun on the other person. I dare say that even if you don't care that much about the other person's life, generally speaking, no legally armed person wants to be known as "the guy who killed so-and-so."
Nor does any legally armed person want the hassle and danger and expense of being arrested and tried for murder.
Finally, if someone with a gun really wants to harm another person, he's not going to use his fists to do so.