The Internet, even more than the media, kills intelligent discussion/thought, by creating enclaves where people who are like minded can engage in massive examples of groupthink, where the most stupid things become established fact in the minds of participants, simply because they choose to be around people who reaffirm what they want to believe.
I think Christians point is that the Internet helps you avoid exposure to other ideas, and reinforce your own. With a normal circle of friends anf family you can't avoid different thoughts, but on the internet you can find a group for the weirdest stuff.
I don't think Intelligence is like in role playing games - drop 18 points in INT, and you are set. There are some physical rperequisites, but still it requires constant training, challenge and exposure. Beer-and-TV controled protohumans can develop quite some brain if challenged.