Bottom line is that in this type of scenario, the principal players are locked in place; Charlie can't shoot the bad guy, but the bad guy can't do much either. There's sort of a mutually assured destruction thing going on - if either one opens the ball, all three of them may end up dead. Charlie is a tough, competent killer in his own right, and he is also a brilliant strategist who knows his opponent well. He knows the guy is a brutal thug who would like nothing better than to kill both the hostage and Charlie as well. So Charlie's going to throw down his weapon? No way. Not at least in the way it was written: with Charlie throwing down his gun and hoping for some other form of intervention. He might throw the weapon away to distract the bad guy (perhaps the best example of this is found at the end of the film Die Hard), but there is absolutely nothing to be gained just by honoring the bad guy's request. Charlie would have to know that, and I think that Garber did his story something of a disservice by trotting out this tired plot device without providing some sort of respectable twist.

(For the record, I suppose I should specify what I think should be the other banned story device. It is when the bad guy makes the hero go someplace with him or her, usually by sticking a gun in the hero's side. Now, this might be okay in a true "thriller" story where the protagonist is a "regular" person. But any security expert will tell you that a person who threatens you and demands that you go with them to a remote location has only one thing in mind: to do you greater harm there than they could do in public. Therefore, anyone with a measure of training in security matters will tell you to do whatever you can right then - that your best opportunity for escape is while you are still in public. If that's the case, why do books and films constantly depict spies or cops or other such protagonists willingly accompanying the bad guy at the point of a gun? Why accede quietly to their threat to do you harm when they're really only out to do you more harm later, and every step along the path only strengthens their hold over you? Sure, it might be fun to show the hero escaping from the bad guy's lair, but why go there in the first place? There must be a justifiable story basis for such a thing, and the "but the bad guy was going to kill him" routine just isn't enough. But that's enough of a deviation from our subject for now).