Full Idea
Emotivists concluded too hastily that because naturalism and intuitionism are false, you cannot reason about moral questions, because they assumed that the only questions you can reason about are factual ones.
Gist of Idea
Emotivists mistakenly think all disagreements are about facts, and so there are no moral reasons
Source
Richard M. Hare (Universal Prescriptivism [1991], p.455)
Book Reference
'A Companion to Ethics', ed/tr. Singer,Peter [Blackwell 1993], p.455
A Reaction
Personally I have a naturalistic view of ethics (based on successful functioning, as indicated by Aristotle), so not my prob. Why can't we reason about expressive emotions? We reason about art.