1. Human beings, by and large, are pretty terrible. If by terrible one means self-interested, self-preserving, suspicious of outsiders, territorial. Another, simpler, way to state it is to state what we all know--human beings are animals.
2. Accepting this premise, we must also accept that human beings, being animals, will do things--again and again--that we enlightened 21st century types can look upon and deem "terrible," "evil," and the like.
3. Human beings, like all animals, do not require a belief system to act on their natural instincts to be selfish and territorial.
4. Human beings, though, unlike other animals have the ability to read, write, and reason in a way that other animals do not. This is not to say that other higher mammals are incapable of reason, but so far, none have really succeeded in communicating with humans and explaining that reasoning.
5. Fair enough. Maybe animals have the concept of religion and we just lack the ability to discuss it with them. Maybe they have other "high" concepts. But still--we're all animals, we operate according to instinct. Biologically, the drive to protect one's people, one's tribe, and so forth, makes sense.
6. Religion is a term that describes a system of beliefs arranged around the presumed existence of a higher power, or a higher order that prescribes and polices certain human behaviors. There are many reasons, historically speaking, that the formation of human religions was useful, helpful, necessary to the preservation of "ancient" tribes of people.
7. Human beings have been fighting and killing one another, wiping out and enslaving other tribes since before language and writing and thus, religion, existed. It's human, i.e. animal, nature. It's what we do.
8. To claim, in whatever fashion, that religion is the cause of most suffering, pain, terror, and bloodshed in the world, is extremely lazy thinking. Human beings cause these things.
9. Religion, then, can be and often has been used as a justification for bloodshed and terror. It did not cause these things. Human beings did not exist in peace and brotherhood for countless millenia, sans bloodshed, until one day, someone decided that there was a God.
10. If you want to blame people for hiding behind religion to justify shitty (i.e. human) behavior, please do so. To blame the concept of religion itself, to blame its Holy Books, to blame adherents of a faith who manage not to commit terrible acts simply because they follow a religion is lazy thinking. It's not thinking at all.
11. Opponents of religion find themselves in a comfortable position to criticize religion precisely because they know that the results of the following thought experiment will never come to pass: What would happen if suddenly, overnight, all religion, all concept of God or holy scriptures were to disappear completely? Would mankind live in peace? Mr. Dawkins can't answer than and he doesn't have to. Neither can anyone who blames a belief system for shitty human behavior. We all know the answer to that question. But we'll never have to answer it.
12. To sum up, people do shitty things because people are shitty. It's hard-wired behavior. It's true that people often use their religious beliefs to justify their shitty behavior. It's very useful in that way. People, on a large scale, do not commit shitty behavior *because* of religion. They use religion to explain their shitty behavior. I understand this distinction may be lost on some. So be it.