{ 1 } - they conflict with how we use language (for example, in ordinary speech it isn't self-contradictory to say "Some things approved by society aren't good").
{ 2 } - they turn ethical judgments into empirical statements (which he dislikes).
{ 3 } - the conventions they propose wouldn't be useful to adopt.

Ayer accepts Moore's refutation of naturalism. He adds that naturalistic definitions fail because they try to define an emotive term (like "good") using nonemotive terms (like "approved by society").