"The 3-month-old baby did not and cannot choose to hike or not to hike. The parents made the choice, IMO, incorrectly".
Correctly/incorrectly is not an absolute value here, my friend. yes, parents make many every-day choices ("incorrectly"?) of whether or not to send a kid to a particular school (where they can be shot), join a football team (where they can get concussions), play with plastic toys (cancer) and eat at fast food joints (a number of bad things). The point is kids make very little choices, and for a good reason. The parents are the ones who make the majority of choices falling back on their own experiences, skill level, and goals; and they are ultimately responsible. By only putting your kid into a sterile environment can you avoid all the potential bad outcomes.
"I hope and pray that others will not use the good outcome to replicate the hike, no matter what their level of experience."
First lets keep prayers for ourselves. I'm sure there is a huge laundry list you want to get done with before moving on to that of others. Second, the others will make up their own mind – no need for anyone what they need or not need do based on your own frame of reference.
".. the effects of even a simple fall by the mother could have disastrous consequences for the child, even if the mother remained uninjured."
An uncoordinated overweight mother can fall walking up the stairs if not careful – shall we test all the mothers in the world if they pass your reasoning and take their children away if not? or should we adjust our "opinions" to the situation, and say she wasn't doing anything that extreme for her own skill level, and prudent enough to turn back when she assessed the risks are high?
"Wait at least until your children have developed some large motor coordination before you take them on the trail."
That child depended on mother's coordination, not her own. At no age (of childhood) would that child's motor coordination exceed that of her mom! mute point.
…now I want to challenge EVERY person who can't bite their tongues but show their great intelligence and understanding of world statistic, child rearing, and logical reasoning: what have YOU personally done for improving the children safety around YOUR neighborhood? How many children that are HUNGRY have YOU fed? How many who are COLD kids have YOU invited to your house? My impression is that you are all so smart online to give advice but have no clue in real life.