In less advanced (or wartorn, or famine-afflicted) societies, where children often die, it is not that the parents do not experience psychological pain at their death that they spend less time grieving or have a more matter-of-fact attitude about it. Just because children are dying all around you does not make the death of your own child any less painful. It's that their lives are an every-day struggle for survival. They can not afford the time and energy for grieving that we in relatively safe places with higher life expectancies tend to feel is necessary. But, not having been able to take the time to grieve and process their emotions about the event, their psychological trauma may manifest in other, seemingly minor ways for the rest of their lives.
Think about it differently. If you have fear towards spiders, being exposed to them will remove that fear. Same applies to trauma and this is actually very well demonstrated. Any form of psychological trauma if the occurrence of a rare event.
This theory pretty much assumes on its face that there is nothing wrong with adult-child sexual relations; that we only dislike it for reasons of irrational, culturally-ingrained aversion. This is patently false. The core reason why we feel an aversion to the idea of adults using young people for sexual pleasure is because it is, fundamentally, an abuse of power that creates psychological trauma, not to mention physical pain and dysfunction for the victim.
Never implied that. In fact we can see your assumption being wrong in many cultures today (and in the past) where children as young as 11 and 12 were getting married. Humans, whether we like it or not, have their sexual organs mature but that age. Ethics is something humans have applied later one. Google age of consent for example and you will find that it varies massively across countries. Again, I am not advocating for child abuse. I am just stating how humans across the planet are treating the issue.
I would argue that in a society where child rape is the norm, individual victims will exhibit lifelong behaviors related to the experience of abuse, even if no one in the culture treats the abuse as legitimate abuse
I would argue that half the "normal" things we considered today as "normal" in 500 years in more advanced societies will be considered abuse since no one will be doing them. Again, the measure here is if everyone is doing it. If a child learns that something is "OK" then they will grow believing that it is. Considering religion for example. People walk with a crucified/tortured individual around their neck. they hang it classrooms. and yet, it is considered "OK".
I think you are mistaken here, as well. Elderly people certainly suffer when their friends and loved ones die, just as parents suffer when their children die. It's just that there is an extra layer of regret and poignancy when a child dies, because she or he was at the beginning of their life and their death is a death of potential.
I used to visit elderly homes and hang our with older people. Sorry, it is much different. Older people do not care that much about death because they have been "slowly trained" to the idea.