I think this is an example of cultural relativism. Since the anthropologist analyzes the action of killing infants under a cultural background and explains this practice from a neutral point of view. For the Inuit tribes, it is very normal for them to kill infants, and they have a reasonable explanation for their actions. Base on their living circumstance, it is understandable for them to kill infants. David also states that infanticide would be morally unacceptable for people who live in a wealthy industrial nation, which indicates that he realizes the differences between different cultures and he is able to understand how different cultures see about the practice.
But on the other hand, people who live in the industrial nation and Inuit tribes have the same goal. They both want to minimize suffering and benefit all people but they just do it differently; they just use different practices according to their own living circumstances. In this case it may not be the example of cultural relativism.