Atheism is a belief that no god exists (in singularity or plurality), and that all that exists on Earth and in the universe at large can be explained by science, even if it's a science/technology that we do not yet possess. This is a definition widely accepted by all atheists. Does it make us somehow superior? No.
I am sickened every time another atheist thinks (s)he is superior over our religious brothers and sisters, just because they believe that no deity exists. By touting the superiority of science and logic over the heartfelt beliefs of religious people, does that not make us as bad as their extremists?
The fact is, nobody, whether through science or theology, can prove or disprove the existence of a higher power. Because of this, we are all, regardless of spiritual belief or lack thereof, equally as clueless about the imperceptible universe.
One would think that atheists, who value science, logic, and reason above all else would be quite tolerant of other systems of belief, largely because science, reason, and logic, as we know it, states that we are not capable of knowing, one way or the other, if a deity exists or not.
Most atheists are quite tolerant, mostly because of the above stated reasons. There are a few, however, that are not. These are the ones that I don't wish to be associated with. They are to atheists what Al Qaeda are to Muslims; what Westboro Baptist Church (the group that protests soldiers' funerals) are to Christians; what the Jewish Defense League is to Jews.
When an atheist proclaims his/her superiority over all religious practitioners, I get sick to my stomach. We are no better or worse than any religious group. At times, I even see my last religious affiliation (with the Celtic pagans) as a more tolerant group. I'll tell you, even for all of their illogical beliefs, they are likely to be one of the most religiously tolerant groups I've ever known (most of my friends still fall into one of the various pagan religious groups - Wiccans, Celts, Norse, Roman, or Greek). Religious tolerance was certainly not one of the reasons I left my former religion. Even after leaving my last religion, I still cherished the tolerance I learned.
I am the type of person that is willing to simply ignore religious displays. As an atheist, I am in the minority here in America. Religious displays are common, even where I live, which tends to be a more secular/religiously downplayed area. I tolerate the crosses all over the place. I tolerate the nativity scenes during the holidays. I tolerate the greetings of "Merry Christmas" and "Happy Hanukkah", which I most often return in kind. At any holiday gatherings I attend, I politely refrain from participating in any sort of religious prayer or offering, and those I know accept that I don't believe the same as them.
As an atheist and a believer in the power of science, logic, and reason, I am what I am. That does not make me superior to anyone. My fellow atheists would likely do well to remember that. We deserve an equal voice, not a superior voice.