I'm personally a religious Roman Catholic, but I'm going to present it from an impartial stance. Oh, and bear in mind that this does not apply to all atheists/theists, in fact only a few, as most are benevolent in their words and willing to discuss things with an open mind. I also understand that other atheists may not have a religion simply because they feel like they do not need one. However, the narrow-minded seem to be the most outspoken, so here we go.
So let's start off by looking a theist standpoint. Theists look at the world, and think to themselves, "Gee, how in the world was this stuff made? How is the earth so perfect for life? Definitely not by anything we can even begin to understand." So theists believe there is a supreme force, namely, God(s).
Now, let's look at the atheist standpoint. Atheists look at the world, and how it is created. They see physics, astronomy, molecular physics, and other sciences, and think to themselves, "This planet is impressive, but we can prove it's creation and the way it works, bit by bit, using logic." Seeing no need for a God to back up their beliefs, they choose not to have one. Hey, why pack extra socks for a weekend trip when you already have 15 pairs?
Now, imagine a group gathering, where atheists and theists, both side a bit extreme in their views are having a theological discussion.
The atheists look at the theists, and say, "What irrational people. They use their God to get away with stuff, all for this 'heaven.'" So atheists consider themselves superior to theists.
Theists, on the other hand, look at the atheists, and wonders, "Why live your life and have nothing to look forward to? Why be so ignorant to believe that humans can truly comprehend all of the happenings in the universe?" Now theists believe they are the superiors to atheists.
Atheists think to themselves, "What logic is there in theism? Since science can be proved and religion can't be proved, why believe in something not proved rather than something that already is proved." Theists reply, "So how did it happen that we are here, alive, breathing, and living organisms, on a perfect planet?" Atheists reply, "Evolution." Theists reply, "Really, then how did evolution begin?" Atheists go on about inorganic molecules, while theists are discussing the improbability of it. Atheists, then, point out, "Just because something is improbable doesn't mean it is impossible. Evolution from inorganic molecules at least is backed by scientific fact. Your God isn't." And the theists are silenced.
But the theists aren't done yet. "Okay, so how did the universe originate? The Big Bang? How did that begin?" Atheists reply, "A superexplosion of a molecule, forming in the lucky organization of atoms, molecules, and eventually, macromolecules." Theists then reply, "Then how on earth did the molecules somehow manage to arrange themselves in their current form." "Simple polar/non-polar bonding rules," the atheists shoot back. The theists then reply, "So how did the molecule that formed the universe come into existence? There had to be something before the Big Bang." The atheists reply, "At least the Big Bang makes more scientific fact than a god." Theists counter with, "Really? On whose research, our own imperfect one?" And the atheists this time hesitate to reply back.
The atheists, however, aren't going to back down. "Okay, if your God truly is perfect, then why does he allow death and horrors?" The theists reply, "It is His will." The atheists have heard this one before. "Oh, so is it his will for murders, diseases, and horror to occur? If that is the case, he is not benevolent like you say he is. If, on the other hand, he can't stop it, then he is not omnipotent. Either way, if one of them is the case, then your God isn't real." The theists, in turn, say, "He is more like a father who allows his son to ride a bike. Every time the boy falls, he gets back up and is now a better biker. It's called experience, and is meant to strengthen one, not diminish one." The atheists, having heard this before, says "We assume a father isn't omnipotent. Why can't God stop these horrors." One of the theists, a Christian, replies, "This is one of the reasons [Christian[s call our God the Father." Both sides stop to reflect on this, but not for long.
Now, the argument is growing heated. A few of the theists say "You atheists are depressing. Where do we go after life?" The atheists reply, "We encounter nothingness. We have nothing to keep us going. You theists, on the other hand, are to much of wussies to believe in a real death." The theists reply, "If we are wrong, then we have nothing to lose. We may have wasted our time praying, but we have done other things to produce goodness for mankind. If we are right, however, you have everything to lose." However, the atheists persist with their argument, and the theists persist with theirs. The argument is now irrational, with the atheists calling the theists war-like and the theists reminding the atheists of Adolf Hitler. The logic preached by both sides is all but gone.
So what is the moral of my story? That there is a counter-argument to every argument, even in religion. When one side believes there is no other counter-argument, irrationalities occur. My point is, don't let people shake you and call your religion (or lack of it) irrational and inferior to your viewpoints. Hold close to it, and don't force it upon others. Remember - you are not inferior or superior to one another because of your religion/secularism. As the old Islam saying goes, "To each, his own religion."