The vast majority of Christians and Jews have never read the bible.
Religion for most people is basically an identity system, not a belief system. You are almost always the same religion as your parents. You don't choose a religion. So rejecting your religion is like rejecting your family, or your tribe.
And since most people know almost nothing about their religion, they defer to so-called experts and leaders who claim knowledge of it. That's why we have extremist leaders and apathetic or inert "followers".
This is a very good point that few people consider. I will point out however that this is the same thing we do with science.
Few people have the time to read enough scientific writings or the ability to understand these writings to draw their own conclusions. We must rely on scientists to review the work of peers and we must trust that this process is not corrupted.
The main difference as I see it is that we are taught from early in our lives to question results of science but are taught to accept religious teachings. In science, if you prove an idea wrong you are rewarded. In religion, if you question authority you are cast-out.
This is really what it comes down to. If you believe that, above all else, God is infallible, as do Christians and Jews, then it is axiomatic to believe that his behavior in the Old Testament is infallible. It HAS to be, by definition, in the same way that a bachelor has to be unmarried.
We could argue it all day, but it won't make a difference. The only way to convince someone that God has done things that are "wrong" would be to convince them that God, as he or she knows it, does not exist.