I realise that many people draw comfort from their personal faith. Unfortunately, once you accept the principle that it's fine for you to insist things are true because you want them to be true, then you have to accept that it's fine for others to do so also. That's when the ugly side of faith kicks in; religious-based terrorism is the most obvious example. But, that's only the tip of the iceberg when talking about the truly ugly things that have been done in the name of religion and justified by faith.
The Golden Rule is inherent within human nature. It's not in religion's best interest to admit this. The claim that you need to believe in a certain supernatural being or outlook on life to be a good person is one of religion's big drawing points. Unfortunately, there's a more insidious reason for this claim.
While the Golden Rule is inherent in human nature, so is the search for loopholes. The most useful loophole is dividing the human race up into those you can do unto as you please and those you have to treat as you want to be treated. Enter religion; since those who don't believe in the same God as you do are evil sinners then they don't deserve to be treated as equals.
Consider, the Hebrew conquest of the Promised Land. You've been wandering in the desert for forty years and suddenly come upon a fertile new land; unfortunately, it's already occupied. What do you do? Well, your Ten Commandants say Thou Shall Not Kill. Fortunately, your God wants you to have this land and the current owners are Godless heathens. Turns out it's all right to slaughter them. See also the European conquest of the new world, the slave trade, and 9/11.
But, comes the objection, what about Nazi Germany or Stalinist Russia? Religion doesn't allow evil to be done in its name because of its supernatural elements. Faith enables a sense of superiority over others that allows one to suspend one's sense of right and wrong. This faith-based sense of superiority can be instilled by a purely secular doctrine also. It doesn't take religion to commit atrocities; merely faith in one's own inherent destiny.