Well, "the Bible" is a complex concept. Not all Christians accepted the Old Testament. Since the very beginning there were groups that saw an enormous conflict between the basic message of the Old and and New Testament. First there were Gnostics and Marcionites, and then many others until Cathars in the 14th century when the Pope said that anybody who kills a Cathar can get their castle. So in the history of Christianity, there were longer periods of (some) Christians not believing in the ST than believing in it.

This distinction is crucial because the ST contains all sorts of atrocities. Modern Christians try to justify them by allegoric interpretations but the logic of this approach is very weak and basically indefensible. Whereas when you don't feel limited by the ST, things become much easier (and a bit more logical).

> Well, "the Bible" is a complex concept.

The "everyone is a sinner" part of it is not, though.