1. The institutions, we as a civilization, have considered "sacred" for thousands of years often are not considered that same way in organized religion, when powerful political forces or massive carnal desire enter the picture
2. Universal rights have been a sticky point for a number of religions because of what particular groups would benefit from them
3. Established religions, throughout history, have been a magnet for would-be messiahs, and an opportunity for those clever iconoclasts and tricksters to create their own new "religion" to challenge the old ones; and finally,
4. Any group calling for "Heavenly Peace on Earth" often has ended up killing millions of people in their fervor, and even stranger, the greatest conqueror in human history actually allowed religious tolerance in an truly unprecedented manner that, even today, we have not seen over most of our planet.