Utilitarianism, Bentham and happiness

To clarify the point regarding happiness. Bentham argues for the minimising of pain and the maximising of pleasure as the source of the calculus of utility. J.S. Mill changed the formulation to refer directly to happiness. Bentham has achieved a fair measure of his aims as his lobbying of parliament laid many of the foundations for the more measured system of criminal punishment that we have today. The excessive punishments that were commonplace in his time now only exist in Islamic countries and are correctly seen as barbaric in their offence against utility - why should the punishment cause more suffering than the crime?