First, let's start with the opportunism of Evangelical Christians. The Colorado shooting is only the most recent exploitation of tragedy used to fill the pews of churches. Pretty much any shooting will get this kind of response, but the interesting thing about the man from Colorado is that he is a devout, active Christian. So, when evangelists like Rick Warren and politicians like Rep. Louie Gomert say the attacks are caused by trends of declining religious devotion, the rise of atheism, liberalism, the ACLU, evolution, gays, or anything else they don't like, one has to wonder if there is anything they won't say to gain supporters (read "money"). Disgraceful.
Prejudice against non-believers has been a religious staple since the Dark Ages; in fact, that was one of the key characteristics of the Inquisition. Suppressing nay-sayers is one of the ways tyrants maintain power. If you can control the masses so that they only agree with you, while simultaneously villainizing the opposition, even if someone challenged you, the masses would remain loyal to you. During the McCarthy Era of the 50's, Communists were villainized in this way. It wasn't about their politics--they were morally bankrupt and evil.
Today, Atheists are the new villains. According to recent polls, Atheists are as trusted in our society as rapists. Think about that for a second. In our society, many people equate those
who don't believe in god with those who forcibly have sex with other people. This reveals amazing prejudice! I have touched on morality before, and have shown how a belief in god is not necessary to be a good person, and, yet, a huge chunk of our society seems to think Atheists are as evil as rapists.
It is true that Atheism is on the rise. In fact, according to a recent article in USAToday, non-believers have reached 19% in America, which makes it the second largest minority in the US, after Catholics (larger than Baptists, Jews, Mormons, Gays, Blacks, etc., all of whom get more respect and representation in politics). It is also true that this poses a threat to religious leaders and their ability to fill the coffers. Hence the opposition.
Another reason for the alarm theists have concerning the rise of Atheism is that other surveys show that atheists know more about religion than religious people do--even about their own religion. So, some postulate that as our society becomes more educated, and information becomes more readily available (via the internet), fewer young people will buy what pastors and priests are selling. As a result we will likely see an increase in the attacks against atheists and non-believers proportionate to the decrease in religiosity. Afterall, desperation makes people say and do incredibly stupid things.
Just listen to Pat Robertson and Jerry Falwell talking about 9/11:
Here is Pat Robertson exploiting the earthquake in Haiti: