One of the most frightening aspects in religion today is Fundamentalism. This reaches into all three monotheistic religions, and beyond them. One recent example of many is Westboro Baptist Church, Topeka, Kansas. It was featured in a 20/20 feature that can be seen here: http://youtu.be/50r0CnKq7_k.
In the feature, we’re introduced to a family and to a church who believes that it is their mission to tell those with whom they disagree that God hates them and they are going to hell. As is the case with every example of Fundamentalism, the presenting issue is rooted in how their sacred texts are interpreted. In this case, the interpretation of the Bible includes the view that God hates homosexuals and people, including American soldiers, who defend a country where lifestyles such as this are permitted.
The most telling part of the feature, and of the Fundamentalist phenomenon within religion, is how this approach affects the people who are involved. In this family, the oldest daughter ends up disagreeing with some of things her family and church believe. She is immediately voted out of the church and disowned by her parents. Perhaps these kinds of visible and self-produced results of Fundamentalist approaches, and not arguments questioning how they interpret sacred texts such, are Fundamentalism’s greatest and most effective critic.