With competent execution, this could be a great children's book! The premise is not realistic—no sane parent would conclude their child is _literally_ a walrus _because he said so_—but it's a kind of non-realism common in children's literature, attributing simple, caricatured motivations to characters in order to tell a silly, memorable story. If there happens to be an obvious parallel between the silly, memorable story and an ideological fad affecting otherwise-sane parents in the current year, that's plausibly (or at least deniably) not the _author's_ fault ...
With competent execution, this could be a great children's book! The premise is not realistic—no sane parent would conclude their child is _literally_ a walrus _because he said so_—but it's a kind of non-realism common in children's literature, attributing simple, caricatured motivations to characters in order to tell a silly, memorable story. If there happens to be an obvious parallel between the silly, memorable story and an ideological fad affecting otherwise-sane parents in the current year, that's plausibly (or at least deniably) not the _author's_ fault ...