The foundational work that imago Dei does for dignity is, in my opinion, indispensable for generating the sort of strong moral constraint associated with rights – and for overriding the temptation to demonize or bestialize “the worst of the worst.” This temptation is so natural that it can only be answered by something that goes beyond our attitudes, even beyond “our” morality, something commanded from the depths of the pre-political and pre-social foundation of the being of those we are tempted to treat in this way.
You can read more of Jeremy Waldron's interesting discussion of the topic here.
