Secular religion is filled with dogma; that is the real problem, unquestioning adherence to some set of unproven beliefs or principles. Dogma pervades both secular ideologies and religious ones. Atheism is the mere absence of belief in deities and whilst it is true some people choose to organise themselves around their atheism that still doesn't fit the standard definition of atheism. The vast majority of my friends are atheists for example and we never talk about it, much less organise anything around our shared atheism. Dogma, be it Communist, Fascist, Christian or Hindu is dogma. As I said, all these belief systems share a lack of evidence and a lack of demand for rational enquiry.
The same people hold science up as religion.
People like to think that science can explain everything.
Which it can't and which scientific method is strictly against.
The scientific method is the based on finding flaws in what is existing theories.
Almost all of the greatest advancements in science are based in this.
Examples of theories that people and almost all atheists hold as true are evolution, global warming, the big bang, the extinction of dinosaurs.
If someone speaks against them their are now considered crazy, however the basic premise of science holds that they are not true and that a better theory exists.
As for atheists killing an abortion doctor. Maybe you should look at Columbine or Virginia Tech. Atheists do some strange stuff too.
Most of all though murder of this type has more to do with mental illness than religion.