" You believe what is quoted above, but do you also believe that their bringing up their children as Quakers and teaching them their "principle of non-violence and humility", which the Quakers say has biblical roots, is child abuse?"

Let me clarify this for you. You can't automatically become a Quaker. There are many who have been brought up by Quaker families that aren't Quaker, Richard Nixon for one.
To become a "Friend" you have to be accepted by the Quakers as being one of them.
Children do not automatically apply. They don't indoctrinate. They have their principles of non-violence, and many don't believe in Christ. Many Quakers would disown the idea of "biblical roots" and this is one reason they were persecuted by Puritans. You couldn't become a Quaker (Friend) just because you wanted to.

"Child abuse"occurs when a child is subjected to forcible training without the intellectual development to make a choice as to what he would believe or not believe.