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."