Allowing children to read poems

In 1954, the book The Little Engine that Could was published. Its message was that if the little engine only believed in itself (by repeating "I think I can; I think I can"), then it could accomplish its task of bring toys over a big hill. Search online for and read the Shel Silverstein poem "The Little Blue Engine," which is a reaction to the book. What are your thoughts about allowing children to read poems like this? Should children only read stories and poems that have a moral lesson? Do you think this poem has a moral lesson?