Recently, on Facebook, I was asked why I couldn't just believe that Barack Obama was acting with good intentions. This was my reply:
Let us imagine that I invited you to be the guest of honor at a dinner held at my house. You enter my house to find the members of my family rushing to put out a greasefire with boxes of baking soda. You immediately step in their way to dump a bucket of water into the grease fire, spreading it all over the kitchen.
As my house burns down around me, I am unlikely to be impressed with the idea that you took this course of action based on "the best of intentions": not only has putting water on grease fires been proven to be a bad course of action with disastrous consequences, but stepping in the way of a family attempting to save their own home is unconscionably arrogant.
If I also happened to know that your every acquaintance believed that all houses should be torn down and everyone forced to live together in caves--some of them having gone so far as to bomb contractors' offices--and that you had attended services for 20 years in the Church of Houses are Evil... then I might begin to wonder what it was that you considered "the best of intentions."