Why might carl sandburg have placed an emphasis on politeness among the animals in the committee of sixty six and in the interactions the animals have with humans in "how the animals lost their tails and got them back traveling from philadelphia to medicine hat"?

I believe he did that in order to teach children how to interact with adults.
He was aware of his own surroundings in which children were impolite towards adults so he wanted to show what happens in the animal world. He wanted to portray young animals as polite and respectful, unlike human children who were unruly.

What passage? there is none

You only say that cause i’m not around, not around