That's a really quaint and convenient way of looking at it when you aren't in a situation where tensions are high and adrenaline is flowing. The fight or flight response is really strong in such situations and people could choose to do either, even at random.
Wait wait... so you're saying if an assailant has a gun and you know his motives are to rob your store, you should always shoot to kill?
Saying you don't sympathize with robbers is not that different from saying they had it coming, especially if you haven't even waited to hear the results on who fired the first shot. If the store owner fired first then it he was he who escalated the danger of the situation, not the robbers.
I am surprised you are drawing conclusions without appropriate evidence.
Your question is a loaded one. It really depends on the situation, but if the person with the gun has specific demands, then they are only using the gun to enforce those demands, and not to kill you. The threat of death is just a device to get you to comply. Robberies almost always go down that way.
If someone comes up to me on the street with a gun and demands my wallet, I give them my damn wallet and let them be on their merry way. My response would not be to draw a firearm and shoot at them, potentially committing murder OR getting myself shot back at in the process. You may feel righteous about it, like you have a right to punish them, but that is simply foolish. Your wallet is meaningless compared to your life.
When it comes to that kind of situation, there are no real guarantees. But if the owner fired first, then he's the one who made the situation more dangerous, not the robbers, and he is to blame for his own injuries as well as the deaths of others.
And AGAIN, I'm saying, that just because someone is holding you at gunpoint does not mean they are necessarily going to shoot you. In fact, complying with their demands will probably lead to you surviving the situation. Your advice of shooting automatically is completely stupid. That just puts you and bystanders at risk.
Any police officer with training will tell any member of the public that if someone pulls a gun on them and demands money, to just give over the money and not fight back. You may be trained in how to use a gun but that doesn't mean you are trained in diffusing hostile situations, and just because you have the ability to fire the gun first does not mean you will get out of it alive.
That is just arrogant and stupid.