Mike,
If you're looking for people's opinions of the government's motivations, why limit your input to "supporters only"? It would seem more relevent to gather data where it exists, and parse it into pro and con later.
I'm certain that everyone would be happy to declare his or her position if there is any likelihood that the answers alone aren't sufficient.
My $0.02
Marx: Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong remedies.
Lennon: You either get tired fighting for peace, or you die.