My question is one I see constantly debated for picture books: Is it a crime
to write in rhyme?
No, but it is a crime to think that rhyming is the same thing as writing poetry, or that poetry is easy.
Thinking that a picture book for any age can be rhymed is a misdemeanor. Letting the rhyme drive the content instead of the other way around is a felony, and sing-songy rhyme that teaches a lesson can be prosecuted as second-degree manslaughter.
Rhyme has serious ramifications, and should not be attempted by amateurs. Even if it doesn't result in jail time, it is often grounds for a restraining order, and certain particularly pernicious couplets have been outlawed in some states.
If you want to see some examples of rhyme done in a law-abiding and publishable way, simply visit your nearest bookstore.