And what it is that trying to prove? Quoting something from the bible doesn't make it true.
It wasn't trying to prove anything. It was a saying attributed to Jesus which seemed to support Gordon's view about humans not being born with sin. It seems to suggest that small children were more 'pure of heart' and less motivated by the self centredness of adults and adolescents. It is a theme which appears in the words of others from other backgrounds.
Upanishads Let a Brahmin reject erudition and live as a child
Black Elk (Holy Man of Oglala Sioux) Grown men may learn from very little children, for the hearts of little children are pure, and, therefore, the Great Spirit may show to them many things which older people miss.
Sri Ramakrishna [19th C Hindu saint] So long as one does not become simple like a child one does not get divine illumination.
Takuan (16th Century Zen Abbot) Zen is to have the heart and soul of a little child.