I have looked at quite a lot of history throughout my lifetime and i am very angry at the un-needed destruction that has been caused by religion. I have many things to go over about it. Let me go over the over all destruction. According to research, math and historians, if medieval Rome didn't adopt christianity, the internet and other futuristic inventions could have been invented by the ~1400's! By now we would be 'traveling the stars'.
There were many things that religion (particularly christianity) has blindly prevented to get us to advance the way we should have. ~200 BCE, the library of Alexandria was constructed. It was three floors high (technological wonder at the time) and was the size of a semi-large shopping center. It had almost all the knowledge known to the European and west Asian civilizations combined! Every year it would gain more and more knowledge. But in 391 CE, a group of (you guessed) christians went on a mission from "god" to destroy the library in order to capture the whole of Egypt! They (obviously) lost the mission but they did destroy most of the knowledge in the world at the time. Even most of the history known to the world was destroyed with the museum part of the library. At this point in time christianity was slowly being adopted by the soon to be Catholic Rome. The remaining knowledge was in Greece and a minuscule amount in Rome, due its conversion to Catholicism. And most of Romes knowledge was in the library. Once Rome was fully converted, it was against science and that led to even destroying more knowledge. This was a part in history called the christian dark ages. It went for ~500 years and more knowledge was lost then gained in that time. As soon as the dark ages were over, knowledge was scarce but many intellectuals were Enlighting world wide knowledge. This is why the next age is called the Enlightment age.
Around the late Enlightment age we regained all the knowledge we lost (number wise). The Enlightment age went on for the next 200-250 years (depending on location), and then gave uprise to the modern age which kicked off with the first world war and then the second one. As you know, Adolph Hitler was the leader of the opposing team (this goes for everyone these days) and had a mission. This mission was in the name of god to some extent acording to many books and bibliographies about Hitler. This is probably the most well known way religion has ruined the world. The amount of knowledge we have now would be equal to the ~mid 1400's If religion wasn't as powerful as it has been.
Next time somebody says religion is a good force for a good cause with a good history, tell them the opposite, tell them the TRUTH.