It took me a minute to figure out what was wrong with this exchange. Tackling someone is assault--but threatening bodily harm unless someone complies (assuming you're not a cop doing his lawful duty, which Loomis Boy obviously wasn't) is coercion, which is just as illegal as assault.
In either case, Loomis Boy had a gun. In most states, the possession of a gun during a violent crime (like coercion) is a felony.
So a trained Loomis guard (had to have some training, or he wouldn't be licensed to carry) commited a felony in front of a room full of people.
I'm actually having a bit of trouble believing this, especially since our victim, according to his own blog, never once asked anyone (Loomis, REI, or actual police) if they thought he had committed a crime. Would have been the first thing out of my mouth.
But, if it did happen that way, my guess is that the guard, at some level, knew that he f***ed up, and needed to stay on the offensive to keep from getting called for it.