(Previous parts in the series: part 1, part 2, part 3, part 4.)
Merz raises the unbelief of the people of Nazareth as an objection to the historicity of the infancy narratives. What should we make of the passage she cites, Mark 6:1-6?
Mark refers to the general unbelief of the people of Nazareth, but adds the qualifier that some were healed (6:5). Given the association between faith and healing in this context (Mark 6:6, Matthew 13:58), the implication is that some people in Nazareth did believe in Jesus. Since Mark's references to the unbelief of the Nazarenes are generalities that allow for exceptions, there's no reason to conclude that only the people healed in verse 5 were believers. There could have been more. The majority of the Nazarenes were unbelievers, but a minority of unknown size responded positively to Jesus.
What about those who didn't believe? Merz seems to think the people of Nazareth would have known about at least some of the events in the infancy narratives if those events had occurred. And they wouldn't have reacted to Jesus as they did if they knew of events like those in the infancy narratives. Therefore, their reaction to Jesus is evidence that the infancy narratives are unhistorical.
We shouldn't think that if the narratives were historical, everybody at the time of Jesus' adulthood would have known about all of what those narratives report. Different people would have had different levels of knowledge under different circumstances. What would most of the people of Nazareth probably have known at the time of Mark 6 if the events of the infancy narratives did occur?
They probably would have known about Jesus' Davidic ancestry and Bethlehem birthplace. The ancestry of the family would have been discussed to some extent even before Jesus' life began, so there wouldn't have been much suspicion that the ancestral claims were fabricated in order to promote Jesus. It's unlikely that Jesus' family would have even attempted, and even more unlikely that they would have gotten away with, changing their ancestral claims from non-Davidic to Davidic after Jesus was born. Similarly, a lot of people in Nazareth would have heard that Jesus was born in Bethlehem and would have known that Joseph owned property there, that Jesus' family sometimes visited relatives there, etc. But many of the other issues addressed by the infancy narratives would have been less known or open to more doubt by the people of Nazareth. Much of what the infancy narratives describe was of a highly private or highly anonymous nature (dreams, Herod trying to execute a child whose name he didn't know, etc.). We don't know how much Mary, Joseph, and other individuals involved told other people. They would have had motives for being highly selective about what they said and to whom. And whatever the people of Nazareth were told, how much would they have believed? I address issues like these in more depth in a series I wrote in 2013 in response to arguments like Merz's.
Let's assume that most of the people of Nazareth knew about some of the events of the infancy narratives, but not all of those events. To get an idea of how complicated that sort of scenario can be, think of the virginal conception. Mary and Joseph would have had reason to be highly selective in what they said about the subject and to whom, if they said anything. Not only would the claim of a virginal conception be met with suspicion, but the premarital timing of the conception, involving a woman engaged to be married, would have made the claim seem doubly problematic. Joseph and Mary may have been perceived as dishonest or evasive in how they handled the situation. If they suggested to anybody that something supernatural had occurred, the claim probably wouldn't have been received well by many people. And the ordinariness of so much of Jesus' life, like his career as a carpenter, was held against him once he began his public ministry. It's easy to see how suspicion, distrust, contempt, and other negative reactions could have been part of the background that led up to Mark 6, even if some positive beliefs about Jesus, such as Davidic ancestry, accompanied those negatives. If the events of the infancy narratives occurred, it seems likely that there would have been such a combination of positive and negative factors.
To complicate matters further, Mark 6 is giving us a brief summary of how a group of people, not just one individual, reacted to Jesus. Individuals can be inconsistent, and groups can be even more so. Luke provides a lengthier account (Luke 4:16-30), and that account helps explain what we read in Mark.
I suspect what likely happened was something along the lines of the following. The people of Nazareth had only partial knowledge of the events of the infancy narratives and had a wide range of views of Jesus. Some received Jesus well (Mark 6:5), and many were impressed by some aspects of his public ministry (6:2), though they had some initial skepticism for reasons like the ones I've outlined above. Despite their skepticism, they were willing to give him a hearing (6:2, Luke 4:16-27). But once Jesus used that opportunity to (from their perspective) publicly insult them (Luke 4:23-7), they were hardened in their skepticism. Some aspects of Jesus' public ministry were popular, like the ones mentioned in Mark 6:2, but other aspects weren't. Jesus was leading a minority religious movement, calling on people to take up their cross and follow him, and much of what he said didn't sit well with the religious and political authorities of the day. It wasn't just a matter of the people of Nazareth being suspicious of some aspects of Jesus' background and objecting to what he'd just said in their synagogue. Peer pressure would have been a factor as well. Most of the nation's religious leaders were opposed to Jesus, and Nazareth would likely have been a focal point of their efforts to undermine him. Those present circumstances would have affected the Nazarenes' evaluation of the past.
Their comments in Mark 6:3 probably aren't a denial that Jesus had Davidic ancestry and other attributes that would commend him as a prophet, the Messiah, or some other sort of religious leader. In verse 2, they commend him for qualities like teaching skills and wisdom, which they surely would have seen in his life to some extent before his public ministry began. Mark and other sources refer to a lot of positive attributes in Jesus' life that would have been noticed before the beginning of his public ministry (communication skills, high moral standards, etc.). The notion that the Nazarenes intended in verse 3 to deny that there were any such characteristics in Jesus' background is absurd.
The point in verse 3 seems to be that the positive attributes in Jesus' public ministry, some of which they acknowledge in verse 2, are incongruous with attributes they object to in his past, like the ones they mention. Verse 3 is about the presence of objectionable aspects in Jesus' life, not an absence of positive qualities. They thought the negative factors carried more weight.
We often speak that way. If we hold a negative view of a person on balance, we summarize our view of the person by mentioning negative characteristics (e.g., Luke 7:34). We'll acknowledge his positive attributes if we're asked to or if there's some other reason to do it, but it's common to summarize a negative view by listing a few negative attributes or summarize a positive view by listing a few positive attributes. Just as the comments in verse 4 about Nazareth not honoring Jesus are a generality not meant to exclude the exceptions mentioned in verses 5-6, so also verse 3 is a general negative assessment of Jesus' background that's not meant to exclude some exceptions.
Whatever they knew about in Jesus' background that they considered positive, those attributes were accompanied by others they considered negative, and they held a negative view of some aspects of Jesus' public ministry as an adult. Mark 6:2 is likely a summary of some positive characteristics of Jesus' public ministry that the people of Nazareth were acknowledging. They heard about those characteristics from other people, and they witnessed them when Jesus visited their town. They're repeating what was commonly said about Jesus by those who thought highly of him, but they're framing that acknowledgement in the context of their skepticism. Verse 3 summarizes their negative assessment of Jesus' background, but isn't intended as a denial that there were some positive elements to that background as well.
Much more can be said in response to Merz's argument, but I'll refer those who are interested to my series mentioned above for more. In that series, I address Merz's argument as it's found in Raymond Brown and other sources. I go through all twenty-seven New Testament books and the earliest material outside the New Testament and demonstrate widespread corroboration of the infancy narratives in those sources.
(Other parts in the series: part 6, part 7, part 8, part 9.)