Here we are getting to the heart of the matter through these excellent examples. So we would say that the contrast between the young and the adults who are less open-minded is a direct function of how much trauma they have endured in the course of their life through being put on the spot, being subjected to stress, being expected to perform, and fearing the consequences of failure, and perhaps enduring failure again and again, even in their struggles to learn and be accepted by their peers and adults overseeing and judging them, like parents, teachers, and eventually supervisors in a work setting, oftentimes.
Children, being inexperienced and also cut off from awareness of their history, are very much akin to a blank slate, at least in what the conscious level of the mind knows and has to work with. There is a natural trust most children exhibit if they have been nurtured as infants and will think the world can be a friendly place, unless there is a bad experience unfolding in the moment to show them otherwise. This makes them easy to work with but also easy to manipulate and makes them vulnerable to learning bitter truths when eventually they are challenged, confronted, or attacked in some way unfairly and find out about the reality of evil in the world, and that when it strikes there may be no one who can truly protect them, so they are on their own and vulnerable, and this is when inner doubts and fears can grow and cause people to develop a tough exterior to help shield them as a way of coping with their vulnerability.
People greatly fear shame and humiliation from being judged by their peers. This is often a consequence of early trauma experienced during childhood and sets a person up to be fragile on a lifelong basis and prone to have strong emotional reactions to any similar circumstances where they might be put on the spot and in danger of being judged. This can be extremely limiting and will often have a negative impact on career attainment because people will be too fearful to take risks to engage in things like public speaking where they are putting themselves on the line and open to criticism and must have the wherewithal to be confident and think on their feet, and be an effective advocate for something without their emotions causing them to choke and lose their train of thought or be unable to recall key facts and figures needed to marshal an argument or the defense of a proposal, for example.
So here again, the relative merits of being open-minded are a kind of opposite side of the coin from the downside and liabilities created by lack of experience when one might be walking into a trap and be exploited by others, or judged unfairly in some way because they were naive and assumed people were already on their side and were not expecting a personal attack of some kind, and when that happens may be shocked and wounded in the bargain. Over time, they will close off and close down, given enough wounding, to simply protect the self and survive. Here again is a healing need that could be extremely valuable if done effectively.