People have been radicalized by all kinds of things: religion, crowds, friends, books, and likely broadcast television too. The amplification capability is just more widely available and there's more fringe content.

Never thought I'd have so many friends and acquaintances who doubt the world is ball shaped, the moon landing, or suspected 9/11 was an inside job. Yet I do and some of them actually came to these beliefs because of school research papers and debate classes.