Probably the greatest argument against the possibility of The Great Cull is the people that seem to appear to believe in it. In this case an impoverished and broken down old man that can't manage his own life.
Gunner can't even manage to pay his taxes never mind manage a "precise and surgical" nation wide project to murder millions of people.
Of course Gunner denies any active part in The Great Cull but stop and think about it for a moment. Would anyone who is smart and wealthy enough, and don't think for a moment that The Great Cull would not cost millions, is going to befriend a down and out bum like Gunner and tell him all the secrets of The Great Cull so that he can blab them all over the Internet?