Straight from the article:

This is a hard one, for liberals only. Do you assume that he is unintelligent because he made policy choices with which you disagree? If so, your logic may be backwards. “I disagree with choice X that President Bush made. No intelligent person could conclude X, therefore President Bush is unintelligent.” Might it be possible that an intelligent, thoughtful conservative with different values and priorities than your own might have reached a different conclusion than you? Do you really think your policy views derive only from your intellect?