No he was not wrong but there's a key word there "armed robbers" meaning they had already threatened the use of deadly force and displayed it. Did he need SYG? No he was already protected and within his rights in all 50 states.
You know sometimes keepin it real, can go wrong. Most people that feel so insecure in our society that they feel the need to carry a concealed weapon with them are unstable and are the 2nd to the last people we want wondering our streets with guns in their pants. Just look at how many stupid situations that have escalated into a murder have occured in Florida since SYG.
I see a big part of the problem IMHO, is someone carrying a gun, by virtue of that act alone, believes that their life has more value than some of those around them.
The justifiable homicide rate has tripled. Maybe you should look at gun death statistics as well.