I think he meant with humans pulling the lever and chickens dying.
Sure, you can do things that you consider evil just to see how you would really react to being presented with such an unpleasant binary choice, but if you chose to do it, was it in fact not evil to you, are you just pathological, or are you perhaps in toddlerhood, where you don't yet really have an intuition for your own relationship with causality, such as it is?