Issue #1: A chunk of the answer was edited out.
Problem: That edit shouldn't have been made.
The editor put in a very nice comment stating "Please, please substantiate strong opinions with sources, or stop making them".
Caveat: I actually agree with the spirit of the editor and disagree with the deleted content to an extent. That doesn't matter.
The proper action would be to comment and/or downvote, not to edit.
To put it bluntly, had I seen that edit in the review queue, I'd have rejected it.
Issue #2: the edit reason in comment seems - sorry to be blunt - incredibly hypocritical and inconsistent with handling of other answers
Problem 1: 2 other answers in the same Q are flat out awful. One merely got a polite "please expand it" comment from the moderator with no further action. One got no attention and tons of upvotes despite explicitly violating Meta-established site guidelines
Problem 2: the editor posted their own answer that contained "strong opinions" without sources - and unlike the linked answer, the editor's answer wholly hinges on those strong opinions.
I have explained the meat of why that is on the editor's own answer in my comments. But the short version is that they say: "[A] Fairy tales have benefits to child development. [B] Discussing them with 10 year old ruins that benefit. [C] 10 year old is incapable of understanding the social complexity of that discussion". "A" is documented very well. B and C aren't documented at all, and without B and C, A is irrelevant to the question.
NOTE: the poster disputed my assertion of lack of backup in an answer, and I'm backing off this specific claim of Problem #2 since I need better documentation to be sure which of us is correct.
Issue #3: After 2 rollbacks, the post in question was locked.
On one hand, locking as a result of edit war is not unheard of.
On the other hand, locking by the person who started the edit war - and who, as (IMHO) made an invalid edit in the first place - is not a very good idea -at the very least, as far as optics (I won't go as far as note the problems beyond optics as I'm not privy to the circumstances of what exactly happened. But clearly, the poster felt extremely wronged by the moderation action).
UPDATE: Lest it appear that I'm picking specifically on the answer by the editor - at least 2 other answers in that post are awful (one based on totally unbacked up statements of "fact", one violating site guidelines of not criticizing the OP).
UPDATE2: For comparison, see how a far-far worse and less substantiated answer was handled on the same question: https://parenting.stackexchange.com/a/20132/604. A mere polite comment. That's it. That's how the answer in question should have been handled, too.