I would presume that it is because small children naturally practice the most basic morality before the religious world corrupts it. They naturally do what is good for themselves and refrain from doing what is bad for themselves (though often they do not know the bad consequences of an act, and they have to learn to do what is good for society as well).
It is only a matter of time before a child that is particularly intelligent and that is trying to stay in this free state of thinking as long as possible is going to make a fully integrated comment. The washtowel paragraph blatantly contradicts what is good for self or society, or what an earlier washtowel (or the Bible) said. The child comments on it, and it throws off the congregation. Many adults are stumbled by this child, who is too young to get baptized (only 3 oe 4). And several turn apostate.
Which is why the Filthful and Disgraceful Slavebugger is trying to control them. The hounder-hounder made yet another additional rule expounding on this, limiting it to a specific number of child comments per study.
I bet they never thought of me as being child-like, because I would mimic Blondie and make a comment that would highlight a blatant contradiction between the washtowel and a previous washtowel, the Bible, or core morals.