I believe that
currently, religion has more negative than positive effects on society. Firstly, religion intrinsically promotes rejection of different beliefs. It tells adherents that
this is the way that you should live life, and it is the right way. This attitude promotes closed-mindedness and intolerance. By attempting to explain many things about the way humans came into being, the vast majority of religions brainwash adherents by giving them false explanations of the natural world. Many people, when questioned as to why they believe something related to their religion, cite their holy book (Bible, Quran, etc.) as evidence. The problem is not only that these books were written thousands of years ago, but also that there is no evidence as to who wrote the books and what the intention of them was.
So when people believe in religion, they are believing something with no evidence to back it up, and these people often let the principles of their religion govern their behavior and attitude towards other people. When pressed further as to explain their beliefs, many people explain that they believe in religion because they were raised to. This obviously does not apply to everyone, but I was watching an excellent video clip the other day of
Richard Dawkins explaining some of the fundamental concepts of evolution to students at a religious school in England. The results were shocking. So many kids rejected the overwhelming evidence for evolution simply because they were not brought up to believe it. Such is the adverse effects of religious indoctrination.
Irrational interpretations of religious texts often set back progress in today's modern society.
If my parents were devout Christians, I would probably not be alive today. I was conceived via IVF, which many Christians oppose. Gay rights have also been severely limited in many nations because of religious beliefs, even when the evidence proves that homosexuality is not a choice, and that it cannot be cured. The list goes on and on. Abortion, birth control, and evolution are all actively rallied against by many religious people who reject it simply because of what their holy book (remember, it is not reliable at all) says.
Many people allow religion to dictate their lives and form the moral basis for their behavior. In fact, this is what I believe is one of the reasons why religion became popular in the first place. Many people are unsure of themselves to the point where they cannot develop a complete moral framework to guide themselves. Religion helps with this by providing one and giving incentives to people to do follow that framework (i.e. a place in heaven). For many people that are 'lost' in life, religion helps them find themselves. But that's where the positives end. Religion is the basis behind such illogical punishment systems as Sharia law. People take religion so seriously that many try to impose their beliefs on others (see missionaries). I would be OK if they were advocating for greater scientific literacy, but religion is the antithesis of science. Though many argue that lots of science is in the Bible or Quran, the fact is is that that is very outdated science. The vast majority of science from back then is obviously not accepted now.
I could and would like to talk more fluidly and coherently about this, but I'll end here for now. To sum my views up, i believe that religion has had adverse effects on today's society because it encourages close-mindedness by singling out a moral framework as entirely correct, holds scientific literacy and progress back by attempting to fill in unanswered questions pertaining to the world with illogical, unsubstantiated (yet commonly believed) answers like the presence of a god, and is frequently irrationally extrapolated into many situations in life.