If a case record were to be made of the world, a somewhat startling trend may be observed. In more than a few instances in humanity's history, actions have been made and claimed in the name of God. These actions have also been, coincidentally, on the side of atrocity more often than not. This may lead one to inquire:
A primary example, and a decent starting point, would be the Western Expansion of the United States. It is known that with this growth, the destruction of an entire people was a side-effect; Native Americans were enslaved and killed in the process. This entire movement was being pushed by those in power as "Manifest Destiny", the notion that God was behind them and this was what they were meant to do. Similar justification was being employed vastly in Biblical times as well, and the issue was directly approached.
No matter what the era may be, the name of God is a powerful force to invoke. If one has a personal desire and wishes to act upon it, there is nothing with as much sway or puissance as the name of God. Whatever one may wish to do, justifying it by blaming it on God (as opposed to taking responsibility for one's own thoughts) is a simple way of shucking off responsibility.
The Crusades, another instance of this, began as something genuinely respectable and righteous. The goal was to spread the word of God and the gospel of His Son, Jesus Christ. It was a simple pursuing of what all Christians were implored to do. However, humans, being the greedy creatures they are, adapted their own desires and wants. The Crusades then became a means to appease the greed of a few, instead of what it was originally meant for. The name of God was not for a moment dropped from the declared reason, and was promulgated as the reason for the murder, the war, and the thievery.
Man has a tendency for corruption, true, and in the pursuit of one's own dreams, the key to the path of least resistance is found in the name of God. None will argue with God, either out of reverence or out of disbelief. When the name of the Almighty God is called upon, it has a powerful sway and any height of greed may be justified with it. Whether God is truly behind something or not, the chimaira of His approval has a strong effect allthesame. See the works of man as man's, riddled with corruption and inconsistency.