Because Paru puts redpilled topics usually avoided like the plague or criticized by """"people""""
The discrimination between carnivores and herbivores. Halfblood and racemixings getting the worst treatment, especially by cops and the secret forces. And it's still the tip of the iceberg, look up the rapes and sexual attempts.
The thing is, those things illustrate animal society the best and I personally read Beastars for it. It doesn't try to do any bullshit and just put the best picture it can if animals were to form a civilized society complete with its flaws. Having the MC being the best example of its worst kind just tops the cake. Plus his autism.