Requiring delegates to be bound is a threat in itself.
I wonder if these fans of bound delegates would feel the same if something came up that so damaged Mitt Romney between now and the convention that all knew that he could never win the election yet he refused to step aside.
In an age of politics where honor and manhood and doing something so shameful as to become an outcast are outmoded concepts, I doubt anything could ever come up that would cause Romney to step aside. So the fans of bound delegates have nothing to worry about there. (and I guess I just avoided addressing your interesting hypothetical of how they would feel there!)
The concept of a political action committee (which is all a state party is) requiring delegates to sign a contract to vote a certain way at a convention is repugnant to our system of representative self-government and a rejection of our origins.