Power corrupts. If the Church is given too much power, it will become corrupted. So to keep the Church in line with the teachings of Christ, we must make sure that it can never have temporal power. Religion has its place and politics has its own. These two should not be mixed together or the result would be catastrophic.
There is a fundamental difference between Jesus and Muhammad and their teachings. When the Jews brought a prostitute to Christ and asked him what to do with her because the law says stone her, Jesus said, let the one who has not committed any sin throw the first stone. This is a great teaching. To be happy as human beings, we don't need lots of laws. All we need are few good teachings and this is one of them.
