No, what I disagree with is his inconsistency, and also his manipulatability by the Russians, who allegedly told him a nuclear war would erupt if he didn't do what they said.

What's to stop someone else from otherwise manipulating him to not stop the asteroid, using similar threats or similar reasoning? Perhaps he finds a way to survive for a time off planet (or sufficiently deep underground), for example. He's the kind of unstable that might result in him not therefore caring how the rest of us fare.