I love insects and reptiles because they are generally presented as evil, and evil, like insects and reptiles, is cool, simply put. Mammals are generally dull as dirt; there is little excitement to be found in the familiar, the safe, the understood. Not to mention, milk and hair are just absolutely disgusting on a conceptual level. I do appreciate gorillas, bats, and bears, though. The Predacons had the better animal lineup without question (the best Maximal is the hammerhead shark from the toyline, and I do appreciate the idea that sharks are folded into heroes with the rest of the fish). You absolutely can have heroic reptiles and insects, but they just don't click as well as villainous ones do, aesthetically or narratively. However, this should not be taken as justification for the ridiculous idea of seeing any animal in real life as moral or immoral.