mob mentality

There are a few ways, but the first and most obvious one is the desire of the characters to "join" the rhinoceros herd. This is a classic example of mob mentality, where merely conforming is more comforting than being right or standing apart. It is a direct metaphor for Nazism as well.

Other ways that conformity is expressed is through the use of bad logic. Each time a character uses bad logic, he or she becomes more rhinoceros-like, and kills off part of the innate humanism that makes us people. Thus Berenger is the only one left standing at the end, a beacon to all that we need to use our own logic and not be influenced or confused by others.