yes, there were some unfortunate events/wars triggered by religion which were devastating for society. However, being a fellow atheist, I still respectfully disagree with your point of net contribution to the society. There are billions, probably 4-5 B, of people who believe in religion in a good way (with out extremism) and I am confident that most of their behavior would be very different if they were not influenced by religions from their childhood so in broader sense, I think the net contribution is still positive.

Religion is helping us to regulate many people's behavior. It will still be very difficult to govern most of the countries even these days just based on law. Probably, developed countries like USA, Western EU where literacy rate is high and are full of all resources can still function just based on constitution/Law but still it would be very different and difficult. Humans are selfish by nature, think about it, what would be the situation like if there were 4 Billions people in this world who were always trying to cheat each other and just thinking how they can get away from the law?

It is also helping the society by making people more selfless, co-operative and generous. Not that Atheists are not generous but I mean, religion helps create more people to donate who otherwise would not have done so.

Probably it looks strange to see two atheists discussing on whether we need religion or not but its fun! and I like healthy discussion.