I once stated that because the Bible is contradictory and preaches hate and violnece and because the Christian church is fragmented that this was proof the words in the Bible couldnt have come from God. Someone replied "according to who." whats a clever way to respond to that kind of chanllenge?
Hard core Christians accept everything in the Bible, atrocities and all. You'll probably not get very far in an argument with such a person.
I do agree with where you're trying to go. Much of the Bible contradicts the popular conception of God being loving and perfect. Who is wrong when popular conception doesn't agree with the Bible? (Answer: both -- there is no god!)
If you'd like a stronger version of a similar argument, take a look at Thomas Paine's "Age of Reason". He argued in 1795 that a god would not have used any book to communicate his intent. His argument is still sound to this day. BTW, Thomas Paine was famous during the founding of the United States for his book, "Common Sense". There are multiple on-line versions of both works.
The reasons that you stated to doubt that the Bible is an inspired by God holy book are true, but they are not the only reasons. It is also the lack of any useful or correct information in science, mathematics, medicine and many other areas; as well as, from the standpoint of morality the Bible is absurd.
For someone to say, "upon whose authority do you question the Bible" is the same as saying you need someone's authority to think for yourself. People who do not question "authority" or the answers that they are given by "authority" figures probably do not question the ultimate "authority" figure - God.
If you believe upon the authority of another person then you give them the authority to tell you what is right without question; it is believing something upon affirmation alone. It is not something that you believe because of reasoning and knowledge. When we believe upon the authority of our own reasoning by finding out what the facts are; then our beliefs are based upon our own authority. When you have the understanding and knowledge yourself you will make your own decisions. You don't need an authoritative figure to give you permission to find the answers. You give yourself the permission to know what is right not some authoritative figure who might (are might not) know as much as you do.
Authority can be given but ability is earned. You do not have to give any power to an authoritative figure. You give yourself the power to be your own authority. To act own your own knowledge not someone else's, to express your own opinions not someone else's opinions. By lowering our sense of self worth the clergy and religion try to think for us. If you need an authoritative figure to tell you what reality is then you are not in control. If you are affirming the validity of something for which there is no evidence on the basis of authority and not your own knowledge then they have taken over the control of your mind and how you are using it.
Someone replying, "according to who" is not a challenge, it's absurd.