I don't even want to know what they say about The Giving Tree.
I don't know about socialism, but it does kind of send the message that you have to be like everybody else to be accepted, that if you're better than everyone else, you run the risk of being ostracized for your superiority, be it real or imagined. I think the intended message was probably more along the lines of "share your Koala Yummies with your table partners at snack time" rather than "conform or be cast out;" we're all just over-analyzing a children's book, probably.