It sounds like you gave him too much too soon. When it comes to matters of belief you have to slowly introduce ideas and concepts, and allow the person to hopefully come to their own conclusions (with a bit of direction). Be a guide, not a lecturer. Pulling the rug out from under somebody is a bit unfair, you can't just take things away from people like that without something to put in it's place.

Maybe it's possible to speak to him again with some kind of compromise. The first thing I thought of, for example, is that all modern astrology is based on a book by the ancient greek Ptolemy who translated the original Egyptian hieroglyphs, but he even admits in the book that he couldn't understand 70 per cent of what he was reading (they were most likely discovering astronomy). This lends a bit of credulity without you compromising your position. It's an area where you can give a concession and reach some level of agreement and he won't feel as much of an idiot. Just remember next time when you're destroying his religion, take it slowly and fill the vacuum of what you've taken away with something else...