Larry Boy, it's "goon" because it has to complete the pun at the end: "Hare today, goon tomorrow."

That said, I have extreme doubts that this is anything more than a silly children's song. As someone said, an excuse to act out unacceptable behavior in an acceptable manner, even if it DOES have the moral that you get punished for such inappropriate behavior.

Am I blathering again?

NW