It is true that animals are able to understand their physicality through observation and mimicry of other animals, and that in some cases, they may use reflections to observe themselves. However, this does not diminish the original point of the essay—that animals without access to mirrors still have to rely on third-party assessments of their appearance. This can be a difficult experience for animals that are treated harshly or unfairly based on their physical appearance, which of course includes rats.
Despite the practical reasons behind why humans may be afraid of rats, it is clear that there is an element of irrational panic when it comes to the furry rodents. Have we forgotten that these are the same animals we've kept as beloved pets for centuries? We have not only domesticated them but also bred them to fulfill certain traits and purposes. This suggests that our reaction to rats has more to do with how they look rather than what they are capable of.
Furthermore, there is a difference between fear and revulsion and though it may be understandable why humans are wary of rats, it is a stretch to say that this warrants such extreme reactions towards them. We must remember that cutesy cartoon depictions notwithstanding, rats are still animals, and their presence does not necessarily pose a threat.
The essay does not suggest that humans let the rats take over, simply that there might be some value in appreciating their spot in the ecosystem and recognizing their basic rights to inhabit the earth. The suggestion that they are embarrassed by how they appear is meant to be taken with a wry sense of humor. After all, if rats could laugh, they might be amused by the sight of us fleeing in terror at their mere existence.