Given our monotheistic/atheistic culture with its secular/sacred distinction, I don't think we can fully comprehend just how radical an idea this was. It tore the fabric of society into pieces. The world order depended on the divine realm—multiple deities that needed to be kept happy. That was part of being a good citizen. It's even more radical than not saying the Pledge of Allegiance, or refusing to stand and sing the Star Spangled Banner (both of which I refuse to do and have gotten no small amount of flack for over the years...).
I'm at a loss as to what it compares to...every comparison I think of falls flat.