Drew claims religious people invented doctrines to morally justify killing animals. John turns this around: on Drew's evolutionary morality, survival-promoting beliefs ARE morality — so religion doing this would be moral by his own framework. Also, most non-religious people eat meat too, so religion isn't the explanation.

If morality evolved to help groups survive and propagate (Drew's stated view), then religious beliefs that help groups survive would be moral by definition. Dismissing them undermines the very moral framework Drew uses for his entire video. Also, non-religious people eat meat without religious justification, showing the behavior isn't caused by religious myth-making.