The holocaust and communism are two detrimental effects that come to mind immediately. How many millions have to die before you realize that there might be a problem? Actually evolution makes no judgment calls on these types of events since survival of the fittest is an axiom. When one person kills another or when one race destroys another, that's survival of the fittest. Belief in evolution cannot object to any action because there is no moral standard.
Evolutionists sometimes point out that the church is not guiltless. They point out events such as the inquisition and the crusades and has a very violent and immoral history. Today we have suicide bombers, genocide in the Sudan and terrorism world wide in the name of Allah. So, they point out that religion not only produces similar results, but that religious people do it in the name of a god or religion and believe this justifies their actions. Religion, they claim, must be worse, because people believe that they are doing the will of God.
This view is incorrect. The reason for all the ills, wrongs and evils in this world is due to sin. The Bible, not evolution, defines sin. Those who reject God and accept evolution don't have a moral standard or definition of good and bad that extends beyond thier cultural beleifs. Why is somthing bad, wrong or evil? The evolutionary answer is "Because I don't like it." or "Everyone agrees its wrong." They often attempt to justify moral actions by their evolutionary expediency. Hence, the holocaust, communism, abortion, euthanasia, eugenics etc. The excuse given is that these things come from something inside the individual, not from a religious book, or a belief in God. Therefore they claim that these things are not connected with evolution or atheism, but they say that the atrocities in the name of religion or God have a direct connection with the Bible.
But the fact is that, God's Word condemns these actions, no matter who is doing them. The holocaust, communism, the crusades and the inquisition all stem from human nature, i.e. something inside ourselves. And that "something inside ourselves" comes from? Evolution does not define morality as anything more than a chemical reaction. The Bible does define morality. We know that all those things are wrong because God's Word tells us they are wrong. None of those things happened because God commanded it or His Word demanded it, but through the rejection of his Word or making his Word secondary to an earthly authority. This leaves the door wide open.
Some people say, "I prefer to define my own morality." That is a standard belief within evolutionary thought. However this also a problem. Morality can't come from within the individual. It has to be a standard that exists separate from the individual. Otherwise morality becomes nothing more than an individual choice and allows each person to justify whatever "evil" or "good" they desire. Relegating morality to society only causes good and evil to be defined by the ones in power. Rejection of God's Word is what allows a leader to starve a million people, send them to a holy war, or for a scientist to accept human cloning and eugenics, or even for a sniper to kill an abortion doctor. Morality is not a smorgasbord, you don't pick what you like and ignore what elements you dislike. The evils of the church come from rejecting God's Word and the atrocities connected with atheism and evolution also come from a rejection of Gods Word.
Evolution, begins with a rejection of God's Word. Therefore there is nothing to counter the natural tendency we all possess to do wrong and justify doing wrong.