"A common attack on the Bible goes like this: Man wrote the Bible. Man is imperfect. Therefore, the Bible is imperfect and not inspired by God. This attempt fails for two reasons.
First, it’s not valid (the conclusion doesn’t follow logically) because the 1st premise subtly presumes what it’s trying to prove, that the Bible isn’t inspired by God. What’s at issue is whether natural man is solely responsible for the Bible or whether God worked through men and inspired the text. Since the first premise presumes the conclusion, the approach is circular.
Second, the argument is self-defeating. Consider this reply.
"Your argument is that man wrote the Bible and man is flawed, therefore, the Bible is flawed. If that’s true then it’s also the case that your argument, offered by you, a fallible human being, is therefore flawed. And if your point of view is flawed, then why should I believe it?"
It doesn’t follow that if man is capable of error, then he always does err. If so, then this argument itself would have to be false, because it also comes from an errant human. Taken at face value, this objection is self-defeating; it commits suicide.
It’s not going to be enough to dismiss the Bible simply by noting that "man wrote it." This, in itself, is not a liability." Gregory Koukl
"If you first establish that the Biblical record can be trusted, then the second problem—human involvement is irrelevant. If God inspires it then it doesn’t matter if men or monkeys did the writing; they’ll still write exactly what God intends.
Another way of stating it: God can’t err; the Bible is God’s Word; therefore, the Bible can’t err, even if men are involved." Gregory Koukl
