I didn't watch the entire video, but apparently Ehrman shows contradictions between the birth narratives. When the two narratives are almost completely different and contradict each other and with history, and when the earliest texts such as Mark and Paul seem to know nothing of a virgin birth, a sensible person should probably believe that the birth of Jesus was totally ordinary.
CF defines "Christian" by belief in the Nicene Creed which says "incarnate of the Holy Ghost and the Virgin Mary".
Furthermore, Christians need to be much more circumspect about what they believe to be true. If a Christian has not had any experience of God, then he/she needs to renounce the faith and become an atheist. Even if a Christian has had some apparent experience of the spiritual, he/she should not assume that this supports the specific claims of Christianity (unless it truly does). In other words, if you witnessed a miraculous healing, do not assume that this supports your belief in Christianity. Or if you see a vision of Jesus, consider the possibility that you imposed your own preconceptions on something else.
That's my opinion FWIW
EDIT: Of course, I'm not urging Christians to become atheists. I just want them to think about the reasons for their beliefs.