I don't see where in that statement it is implied that the differences should be attenuated for their own sake, and not because of some negative consequences that that researcher believes altered sleep schedules have. The article itself states that the causal relationship between being a night owl and certain negative outcomes is hard to clearly establish, but the tone of the article suggests that many experts suspect such a relationship.

You may disagree with his beliefs, but to claim that an expert in the field is ignorant, just because his statements don't accord with your own experience, is ridiculous.