In response to the question of why we should act in a moral manner towards other people, Loftus asks on p. 42 "What difference does it make anyway whether people are of infinite precious worth?" He trying to show that Christians don’t have a monopoly on morality.
He can answer his own question in the very words he uses. The word infinite assumes a transcendent moral anchor; God. That means we are products of a divine ethic that is greater than anything any group of people can devise. The word precious indicates something that is necessarily worth preserving.
The word infinite isn’t applicable to people in a non-theistic framework but, does have meaning to theists. The word precious is possibly also not applicable to people from a non-theistic perspective. Many non-theists would maintain that humans are no more precious than any other life form on earth, or the earth itself for that matter. This worldview sees an equality among all things. This would certainly be true of pantheists who believe that everything is ultimately one (Advaita or modern Vedanta Hinduism). Consequently, people really aren’t precious to the non-theist in the sense that they are to the Christian. That’s not to say that Christians only think people are precious and everything else is garbage. It’s just that people have a special purpose and relationship with the creator in addition to the preciousness of the rest of creation (Gen 1:31). In light of this, non-theists can’t lay claim to an ethic that is equal to, much less superior to, Christianity. Non-theists aren’t able to escape the moral relativism that is a logical outworking of such a secular worldview. If relativism is the rule, no non-theists are able to justify their version of morality over another view, including Christianity. The strongest option available to non-theism is that any secular ethic may be applicable in a local sense but, certainly is not universal.