Actually, the question of whether organized religions have brought more peace than misery to the world is more difficult than you might first think.

Obviously, many wars can be laid at the feet of religion. Even more so, if you are willing to stretch the definition of "religion" to include National Socialism or Communism.

On the other hand, when you are not rubbing one religion against another, and looking only within a particular nation and culture, religions are often instrumental in preserving order and peace within that one culture. A specific nation or culture is often held together by religions and customs, preventing much friction and warfare within that culture. That these nations and cultures sometimes are more restrictive than is good for humans is an important issue, but we are talking peace vs. war right now.

There are exceptions, of course. Muslims, Christians, and many others have had no problems fighting others of the same religion, although a case could be made that they were often from different sects of that religion, so might qualify as "one religion rubbing against another." It might be interesting to study this in more detail. How many wars have ever been fought between two nations with exactly the same religions?

If you look at crowded nations like Japan and China, how well would they get along without the strict interpersonal customs and traditions that they have? How much of this is religion, and how much is national culture, is problematical. I'm not sure that with many nations you can draw a solid line between the two.

I know that if China had a culture that had been expansionist, instead of isolationist, over the past thousands of years, that we would be looking at a much different world today.