My friend has told me numerous times that thanks to the Church in the middle ages, we were essentially neutered as far as technological advancements go, and the Church purposely kept people the dark so they wouldn't learn. He has a hatred of the Catholic Church from this. From my understanding this notion is wrong, but I'm not sure of the facts behind it. Can anyone shed some light on this?
There are several answers linked here by /u/bristoneman and others that you might find helpful.
For my own part, the idea that the Catholic Church kept people in ignorance is ridiculous. The demand for educated Clergymen was one of the main drivers behind the founding of the earliest universities, and many if not most of the leading intellectuals of the Middle Ages had some association with the Church. After Fourth Lateran, there is a wealth of teaching texts specifically aimed at instructing Priests on how to preach effectively, so that the masses could understand the faith. There is, in fact, a widespread concern among clergy of all stripes with making good teaching available to more people. In short, the Catholic Church was both the widest provider of education and its biggest sponsor throughout the middle ages.
No, this is a common anti-Catholic myth that originated in two late 19th century American books, Andrew Dickson White's The Warfare of Science with the Theology of Christendom and John William Draper's History of the Conflict Between Science and Religion. As David Lindberg, Ronald Numbers, and John Hedley Brooke have shown in multiple works and edited volumes, White and Draper were promulgating their own anti-Catholic views of history.
There's a lot of good literature here, I guess I'd start with Numbers' and Lindberg's God and Religion: Historical Essays on the Encounter between Christianity and Science or John Hedley Brooke's Science and Religion.