I think this depends on your definition of innocence. For instance, one could mean it as the purity of being more one with nature and base patterns of survival. The convolution of man could easily be seen as something corrupt.
Agreed, corruption tends to be about how something's become a little too human. Even d20 games tend to list animal mindsets as "neutral" from them not having much beyond baseline instincts and personality quirks when compared relatively towards the exaggerated stances humans can take.
In some cases it goes further, such as neoteny. The brain of dogs has been shown to be comparable to that of humans with Williams Syndrome.
So in other words, people with Williams Syndrome are animals?
But why would we want all animals to be dogs?
Likely to feel more in control over them.
The traditional idea of innocence is pretty vapid and boring. I respect and care for animals more because they have the capacity to be "bad".
If "Good" and "Evil" are largely relative, and the species behaves roughly the same across the board, wouldn't each animal need their own entry for what qualifies?