Religious people like to push atheism aside as "just another religion". Atheism is a religion like spectatorship is a sport. That argument doesn't really hold water but i think the real argument is about science.
Is science just another religion? That argument may have credence. We're seeing more and more "scientists" with immoveable opinions about nature and the universe. Science is however steeped in a history of accepted misunderstandings, successful disproofs and new revelations. To that i say; there will always be narrow mindedness due to assumptions resulting from an improving understanding. This is true for both science and religion but science tends to be more resilient to this narrow mindedness.
Years of life experience often leads to personal revelations that are sometimes compatible with socially accepted belief systems. When this compatibility is realised, it has a tendency to create an assumption that the rest of the tenets in the agreeing belief system must therefore also be true. The human need to be part of a community then results in the individual becoming dedicated to finding evidence that fits the belief system rather than adjusting the understanding to fit the facts.
We build our personal and social belief systems on plausibility and the probable validity of information. Beliefs evolve and branch off from one another but we ultimately agree on the base facts and take separate paths from there. The further away a belief is from the base the less plausibility it has. Science is an attempt to strengthen our foundational beliefs and build up from there so that we are more equipped to determine the plausibility of deeper beliefs.
Both science and religion claim to be ahead in their understanding of the universe and it's generally accepted that the weaker one will eventually merge into to the other. Religion is far ahead in terms of a possible explanation of life and the universe but it's probability of validity is almost zero due to many assumptions and unreasonable conclusions. Science on the other hand is far ahead in validity but relative to religion, it's short on giving answers to deep, pressing questions about our existence and our place in the universe.
Science is ultimately another belief system and could reasonably be called a religion. However, science is generally of the understanding that current beliefs could be misinterpretations and even the most fundamental scientific beliefs are always open to re-evaluation. Although science is occasionally guilty of promoting an unquestioning attitude, religion has a far greater tendency of stating "divine truths" and maintaining the taboo of questioning accepted beliefs.
If science is a religion then it's the most effective religion there is at attaining an understanding of the universe. Atheists generally do not denounce the existence of god, they simply realise that the probability of a conscious omnipotent being that influences our lives is so low that it isn't worth investigating at this stage of human understanding. Whether or not any of the world's religions are valid is irrelevant when our fundamental understanding of the natural universe is still in it's infancy.