Rothbard on Utilitarians

Murray Rothbard:

Utilitarians, like economists like to think of themselves as "scientific" and "value-free," and their doctrine supposedly permits them to adopt a virtually value-free stance; for they are presumably not imposing their own values, but simply recommending the greatest possible satisfaction of the desires and wants of the mass of the population. But this doctrine is hardly scientific and by no means value-free. For one thing, why the "greatest number"? Why is it ethically better to follow the wishes of the greater as against the lesser number? What's so good about the "greatest number"?

(From The Ethics of Liberty)