I'm not one of those atheists/agnostics who bash religion as the cause of all man's evil. To do that is intellectually dishonest.
The truth is, we don't know how we came into existence. If there is a Creator, then he or she hasn't made itself known to the rest of us in the past 500 years or so. Eye witness accounts prior to that occurred in a context where it was impossible to record such an event.
But still, religion/belief in God does serve a purpose: it forces people to get along with each other. If all you have is a society where people have sexual relations in the street or where might makes right, then it would degenerate into a big pile of goo.
And yes, I think that restricting humanity's natural urges to express their sexual mores should be regulated. It forces people to be modest -- and even avoid sexually transmitted diseases in some cases.
Is there such a thing as a socially conservative agnostic/atheist? I'm probably the closest thing in that regard. And yes, I think that gay marriage should not be permitted or recognized by society.
Here is the ultimate paradox regarding Creationism: those people who profess to be religious tend to support it and do not believe in evolution. And yet, when one studies the history of religions, it is those societies that were the most religious that were the strongest and were able to impose their will on others. In terms of "survival of the fittest" -- religion is a fascinating study in terms of human sociobiology. Darwinism only barely scratches the surface here.
Case in point: nobody in the world prays to the Greek/Roman pantheon of Gods and Goddesses nowadays. In Ancient Rome, they had beautiful and lavish temples dedicated to them--and now their statues are sitting in museums--a curiosity at best. At one point in the days of Ancient Rome, to insult the Gods was punishable on pain of death. Then eventually, laws against blasphemy were liberalized and the Romans themselves started to question and deconstruct their own religion as a mere superstition.
What happened after that? Christianity took over Rome and almost the rest of the world. The same process that is occurring today with mocking Christianity is the same one that occurred in Ancient Rome.
What religion is waiting in the wings to take over where Christianity left off? Well, the West is getting a lot of immigrants from the Third World. It's obvious that the next great, big religion is going to be Islam--the poor man's religion.
So when liberal atheists/agnostics attack religion -- they are really attacking man's greatest invention.
Religion is part of the human condition.