Probably because, seeing as how Bush is a moral man, they feel inklings of accountability for their actions. THEY DON'T WANT TO BE HELD ACCOUNTABLE.
Plus, GWB is a Christian. And you know what THAT means. (wink wink)
Anyone these days who has the "audacity" to let it be known that he or she is a Christian and that they are serious about their faith in Christ ----- especially if they are in public office-- will be scorned. From then on, it will color everything you say and do. Christ said to his closest followers: "The world will hate you, but remember that they hated Me before they hated you."
[Besides that, they hate him for his family's money, his privilege, and his rich friends. But has their ever been a president that didn't have money or rich friends? They also think that with his verbal blunders and stammers (dyslexia), he is a poor representative of America.]