The problem is that they tend to ignore the human rights of children in places like that. Cutting parts of their bodies off, refusing to give them a proper education, causing them mental illnesses with horrific stories and threats from X-rated books etc.
Children have rights and are not property. Religious people can do what they like, as long as their children's rights are respected.
I do hope you're trolling and not seriously as ignorant as your post suggests. Circumcision (I'm assuming that's the "cutting parts of their body off") was resolved over 1,800 years ago - back in the Apostolic Age. We are told that circumcision of the flesh avails nothing if we aren't circumcised of heart. We are taught that if a Gentile (non-Jew) converts to Christianity, he does not need to be circumcised (indeed, if circumcision is part of the conversion, the convert puts himself under the Law of Moses).
As for the other charges, extremists are dangerous regardless of their creed. My sect teaches that "the glory of God is intelligence" and that our lot in the next life will be all the better the more intelligence we obtain. We invented the modern TV, helped with open heart surgery, etc.