Coleman laid out a map of nine meta-ethical theories. While he had some reservations about it, I thought it was pretty good. There are going to be limits to how a graphical map can capture the relationship among philosophical positions; it’s enough if it helps the audience remember the basic points on which the major views differ.
Concerning emotivism, Coleman thought that one author he read had successfully answered the so-called Frege-Geach Problem. The problem is that moral propositions seem to have truth values when used in sentences that have logical operators like conjunction, negation, and the material conditional. That shouldn’t be so if moral propositions only express emotions without even attempting to say things that are true or false. Anyway, there are a variety of sophisticated attempts to give emotivist analyses of moral thought and talk that answer this problem; Coleman thinks he’s found one.
But, at the same time, Coleman is not convinced by emotivism. That suggests that he finds the other problems with emotivism to be compelling. For instance, it doesn’t ring true: we think we’re saying something true when we assert moral propositions. Also, emotivism is hard to square with genuine disagreements about morality, as there aren’t genuine disagreements about matters of taste or feeling.
One famous advocate of emotivism is A.J. Ayer. I can’t let this go without pointing you to a story about Ayer, Mike Tyson, and Naomi Campbell. That has nothing to do with emotivism. I just thought you would enjoy it. Odd tale involving a famous philosopher, huzzah!