Utilitarians lead to humans to be treated like animals – their logic can make no differential between the live of a human and a sheep

A good man is one who strives to maximize the sum total of happiness and the good society is the society that seeks to maximize that sum total.

Indeed if a contented idiot is as good as a contented philosopher, and if a contented sheep is as good as a contented idiot, then a contented fish is as good as a contented sheep, and a contented beetle is as good as a contented fish. Where shall we stop?

In utilitarian morality, a driver who swerved to avoid two sheep and deliber- ately killed a child could not be considered a bad man, since his action may have increased the amount of happiness in the world. This result is contrary to every ethical intuition we have.

- Richard Posner