It's funny because Bart Ehrman admits Mary was the mother of Jesus but says Joseph was not, so Bart is admitting that Mary cheated on her husband to give birth to Jesus and that also she is a liar. And thus, Jesus according to Bart was born into sin and his true father was covered up. So we have no idea who Jesus' true father was since it wasn't Joseph. Christianity according to Bart is built on fornication and lying about it. The implication is undeniable.