The bizarre category of 'minor'

A couple of days ago, somebody left a comment on my article about why I love sixth graders so much. I'm guessing he or she wasn't a fan of my output, given the comment read:
as I minor I want you to know you are an absolutely sickening depraved person and I think you should stay away from children thx
Now, I'm quite happy to receive hate mail. I find it rather amusing. And this particular comment triggered a desire to write a brief article on an absurdity.
The commenter was likely a 16 or 17 year-old westerner, very different to what I'd imagine when talking about a child or a YF. Such a person is an adult to me, albeit one who has likely been emotionally stunted by the west's outrageous infantilization of adolescents. The presumably intended message of "I'm one of these people and I think you're gross" didn't quite land as hoped!
Of course, the term 'MAP' and its predecessor 'MAA' are very much guilty of forcing the disparate categories of youth under one banner, doing nothing to clear up any conflation of young children with young adults. The intention was to replace misused terminology like pedophile and largely unknown expressions such as hebephile and ephebophile. It also has the benefit of pushing unity across chronophiles, something I very much endorse.
But independent of anything MAP activists have done, there has been an extreme drive to separate the categories of 'adult' and 'minor', alongside the erosion of boundaries between infants, children and adolescents. Infants and 17 year-olds are wildly different, and yet it sometimes feels like people see a 17 year-old having more in common with a baby than an adult. Relationships between 18 year-olds and 16 year-olds are increasingly being problematized; I vaguely recall one instance where a 'pedophile hunter' conducted a sting on such a case.
Not long ago, I visited a very poor country. From a non-sexual perspective at least, the separation of adult from minor was far less distinct. Young people, from the age of 'not going to stick their finger in the electrical outlet', were treated as people. They helped out with the family business, partook in somewhat risky activities without being followed by helicopter parents, and so on. In doing so, they were obviously learning practical skills, figuring out safety boundaries for themselves, and building a sense of self-reliance. There were clear problems linked to poverty; I saw children begging for money and selling items that were of little value, which was obviously remarkably sad. One thing I did notice, though, is that the children overall seemed happier than the rich kids I teach in a wealthier country.
The distinct category of minor, covering such a wide range of developmental realities, is clearly not a good thing for young people. The question for me is, what drives the extremism in western countries?