It also illustrates the trait that comparing a man to almost any animal was considered derogatory...

it could be/read either way. Men are animals, yes, but then again, animals (for all the lack in 'reason') are sometimes noble compared to humans. The faces of the animals here are naturalistic and not derogatory in themselves- seems more like the artist was hoping to shock by inverting that nobility. Same for many animal fables (from Aesop to Animal Farm, etc.)
That said, I haven't seen the text of the rest of the booklet...