I must clarify: I do not believe and I am not suggesting that Religion is the only evil, nor that it is the cause of all evil. There are many other evils (war, crime, prejudice, injustice, etc.) that are the main issues humanity faces today. However, I do believe that religion is a warped mirror that distorts the actual cause and nature of the evils in the world, and therefore warps the way we take action against such evils. For instance, the Witnesses. They believe that when something terrible happens (outside of "time and unforseen occurence"), it is a symptom of Satan and his demons causing the world to deteriorate further and further because they have a short time left, and things can only (and must) get worse. They believe there is no way to fight this or improve it, and because of that they do not take the necessary steps to begin solving the problems faced by the world.
Religion blames evil in the world on an outside source (Satan and his demons) and a made up internal force (inherited sin), stopping any possibility of humanity being able to solve its own problems without outside intervention. This belief is self-defeating and breeds an apathetic population of victims. In order to improve our world, Religion must be let go of so that humanity can honestly evaluate our problems and, most critically, take steps toward correcting them. We only get one world, one shot, and no one is coming to save us. It is vital that we have a clear, rational purpose and sense of urgency in these matters.