I would bet a shiny nickel that had Grisham calmly unsnapped the rifle from being slung across his chest and put it down, there would have been no arrest, no story at all.
You're probably right, but as far as that video shows, there was no reason for the Officer to ask him to do that. Him refusing was legal. Again, you're suggesting capitulation for the sake of just getting it over with quickly and easily. That's the point. From what we can see, he was arrested for not breaking the law. That, in turn, IS breaking the law.
I still can't believe that people are saying that we should just agree to give up our rights just so we don't go to jail. That's absolutely amazing to me.