Dr. Bart Ehrman is a former evangelical who turned agnostic  and now spends his time trying to debunk the truth of Christianity. Ehrman, James A. Gray Distinguished Professor of Religious Studies at the University of North Carolina, Chapel Hill, has written or edited thirty-three books and is a soi-disant “world-renowned New Testament expert.” He is considered to be one of the most clever and dangerous skeptics operating today.
The more one reads from his popular books, however, the more difficult it becomes to accept such a view of him. He traffics a great deal in bald assertions  and shows rather pedestrian thinking. Consider, for example, the following, adduced by Ehrman  as an example of a contradiction in the Bible:
Some sayings of Jesus are rendered in similar but nevertheless diverging ways. One of my favorite examples of this phenomenon is the pair of sayings related in Matthew 12:30 and Mark 9:40. In Matthew, Jesus declares, “Whoever is not with me is against me.” In Mark, he says, “Whoever is not against us is for us.” Did he say both things? Could he mean both things? How can both be true at once?
Seriously? They can both be true if there is no middle ground, i.e., if one can only be for Him or against Him. The Venn diagram is shown below:
If that is not intuitively obvious, we should learn it no later than in junior high school.
Ehrman's Objection to Harmonization
Ehrman has an idiosyncratic objection to attempts to harmonize the multiple accounts of Jesus’ words and deeds in the Gospel books. Regarding Jesus’ cleansing of the temple, Ehrman avers ,
The Gospel of Mark indicates that it was in the last week of his life that Jesus “cleansed the Temple” by overturning the tables of the money changers and saying, “This is to be a house of prayer … but you have made it a den of thieves” (Mark 11), whereas according to John this happened at the very beginning of Jesus’ ministry (John 2). Some readers have thought that Jesus must have cleansed the Temple twice, once at the beginning of his ministry and once at the end. But that would mean that neither Mark nor John tells the true” story, since in both accounts he cleanses the temple only once.
He clarifies this objection in regard to the accounts of Peter’s denial of Jesus, in which Jesus foretells in the Gospel According to Mark that Peter will deny Him three times before the cock crows twice, whereas in the Gospel According to John, Jesus foretells that it will be before the cock crows. “Well, which is it – before the cock crows once or twice?”  asks Ehrman. He then mentions Johnston Cheney’s “very clever solution: Peter actually denied Jesus six times, three times before the cock crowed and three more times before it crowed twice.” Ehrman then objects ,
But here again, in order to resolve the tension between the Gospels the interpreter has to write his own Gospel, which is unlike any of the Gospels found in the New Testament. And isn’t it a bit absurd to say that, in effect, only “my” Gospel – the one I create from parts of the four in the New Testament – is the right one, and that the others are only partially right?
This objection, however, is ludicrous; it is difficult to imagine it being taken seriously. The Gospel books are each of them accounts of the ministry, miracles, words, and death and resurrection of Jesus, but no one of them is comprehensive. Each writer decides which details to include and which to leave out – and that is the way it is with all historical writings; we demonstrated an example  in the matter of four modern-day accounts of an interview conducted after a semi-final game at the 2015 World Junior Hockey Championships. To get as comprehensive a summary as possible of the history of any event, the proper way to do it is to combine what all of the separate accounts record. That is not “writing our own Gospel” – any more than combining the four separate news accounts of the WJHC interview would be “writing our own news report.” Why Ehrman complains about reconstructing events based on all available accounts, which is how historical analysis is done, is very difficult to understand. It does not seem clever at all.
Not content with such an egregious error, Ehrman buries himself further  as he continues:
Moreover, is this reconciliation of the two accounts historically plausible? If Jesus made a disruption in the temple at the beginning of his ministry, why wasn’t he arrested by the authorities then? Once one comes to realize that the Bible might have discrepancies it is possible to see that the Gospels of Mark and John might want to teach something different about the cleansing of the Temple, and so they have located the event to two different times of Jesus’ ministry. Historically speaking, then, the accounts are not reconcilable.
The only actual argument Ehrman offers is the claim that if Jesus had cleansed the temple early in His ministry, He would have been arrested at that time. But this is not much of an argument, as there is no way of knowing whether Jesus’ actions merited arrest; when the order did go out to arrest Him, so that He stayed mainly in Galilee (see John 7), it was not because of either temple cleansing incident. We also know that the Jewish authorities had long wanted to arrest Jesus but hesitated for fear of the multitudes who supported Jesus.
But look again at what comes after that lone, invalid argument :
Once one comes to realize that the Bible might have discrepancies it is possible to see that the Gospels of Mark and John might want to teach something different about the cleansing of the Temple, and so they have located the event to two different times of Jesus’ ministry. Historically speaking, then, the accounts are not reconcilable.
So one theoretical possibility is raised, upon which another theoretical possibility is surmised, upon which a third theoretical possibility is staked, and then – Presto! Change-o! – this edifice of unsupported possibilities magically transforms into the fact – fact, I tell you! – that the accounts are not reconcilable. Trust me, I have a Ph.D. Pay no attention to the men behind the curtain who have indeed reconciled the accounts.
This, folks, is standard operating procedure for liberal Biblical scholarship. It is not clever. Ehrman’s objections to harmonization bear no weight at all.
 Ehrman, Bart D. Misquoting Jesus: The Story Behind Who Changed the Bible and Why. New York, NY: Harper San Francisco, 2005, pp. 1-14
 Countless examples could be adduced. Here is one: in Jesus, Interrupted: Revealing the Hidden Contradictions in the Bible (and Why We Don’t Know About Them). New York, NY: HarperOne, 2009, p. 23, Ehrman asserts that “Mark was probably the first Gospel to be written. Scholars have long thought that it was produced about thirty-five or forty years after Jesus’ death, possibly around 65 or 70 CE.” Ehrman adduces no actual evidence for these claims; “scholars have long thought” and “possibly” seem to be offered as substitutes for actual evidence. Ehrman does provide a footnote here, but that only says, “See the discussion on pp. 144-45.” This discussion, however, does not offer any evidence either. What passes for evidence here is an argument from silence (and one that is erroneous) and the claim that “It also appears that the Gospel writers know about certain later historic events, such as the destruction of Jerusalem in the year 70 CE … That implies that these Gospels were probably written after the year 70.” (p. 145). This offhanded dismissal of the possibility that the Gospel books record genuine predictive prophecies not yet fulfilled at the time of writing show that Ehrman is trafficking in a circular argument here, another logical fallacy.
 ibid., p. 41
 Ehrman, Jesus, Interrupted, p. 7-8.
 Tors, John. “Contradictions in the Gospel Books? Lessons from the World Junior Hockey Championships.” This sort of real-life investigations is what should be – but is not – done by Bible scholars.