"Therefore, since we are the offspring of God, we ought not to think that the Divine Nature is like gold or silver or stone, something shaped by art and man’s devising. Truly, these times of ignorance God overlooked, but now commands all men everywhere to repent, because He has appointed a day on which He will judge the world in righteousness by the Man whom He has ordained. He has given assurance of this to all by raising Him from the dead.' "
Paul tells the people of Athens quite clearly that God has overlooked the past ignorance of those who worshiped idols. While they are now expected to repent and believe in Jesus, they had previously believed in pagan gods because, as Ehrman says, "they simply didn't know any better." And as Paul says to the Athenians, God doesn't blame them for it.
But does Paul really think that? What about the passage in Romans 1 that includes:
"For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, because what may be known of God is manifest in them, for God has shown it to them. For since the creation of the world His invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse, because, although they knew God, they did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened. Professing to be wise, they became fools, and changed the glory of the incorruptible God into an image made like corruptible man—and birds and four-footed animals and creeping things."
Here Paul takes exactly the opposite viewpoint. God "has shown" himself to them, his "attributes are clearly seen," "they are without excuse," and "they knew God." The discrepancy is threefold, as Ehrman explains:
"Do they worship idols out of ignorance? The "Paul" of Acts says yes, Paul in his own writings says no. Are they responsible for their idolatrous activities? Acts says no, Paul says yes. Does God inflict his wrathful judgment on them in the present as a result? Acts says no, Paul says yes."
So here we have two views of God's relationship with unbelievers that are clearly at odds in multiple ways. Either Paul had hopelessly conflicting opinions on this subject, he was lying to the Athenians to win them over, or the author of Acts fabricated his story. Ehrman takes the latter position, saying that "the real Paul would likely have preached some fire and brimstone to get these people to realize the error of their ways." In any case, this example deals a serious blow to the Christian claim that the Bible is an inerrant and unified work.