Didn't see it but I looked at the PBS website. Looks like it's mostly old news. The political/religious interrelationships between the established Catholic church and European dynasties doesn't make for good dinner conversation. (Mixing religion and temporal power is a horrible thing for everyone but the group that's "in".)
Gutenberg and his movable-type press broke the Church's monopoly on literacy. Up until then, heretics could be isolated and eliminated: after that literacy became common outside the church and the heresy could spread beyond the heretic's locale. Thus, we got a Reformation, with Methodists and Episcopalians and Lutherans and whatnot.
Turns out, the protestent religious groups were no more benevolent than the Catholics: see the behavior of the Tudors and Stuarts in England, consider Cromwell, then move on to the various Lutheran princes in Germany, the Puritans in Massachusetts - nauseating. (I'll leave Caliphs and Ayatollahs and such out of this discussion but you can think about 'em if you'd like.)
My first conclusion is that religious authority needs to be kept as far from temporal power as possible. My second is that the ability to read and write is the best counterbalance to religious authority.