According to A. J. Ayer, if one makes a moral judgment like "Stealing is wrong," one is expressing or arousing feelings.

The presence of an ethical symbol in a proposition adds nothing to its factual content. Thus if I say to someone, ”You acted wrongly in stealing that money,” I am not stating anything more than if I had simply said, ”You stole that money.” In adding that this action is wrong I am not making any further statement about it. I am simply evincing my moral approval of it... If now I generalize my previous statement and say, ”Stealing money is wrong,” I produce a sentence which has no factual meaning – that is, expresses no proposition which can be either true or false. It is as if I had written ”Stealing money!!” – where the shape and thickness of the exclamation marks show, by a suitable convention, that a special sort of moral disapproval is the feeling which is being expressed. (107)

Peter Geach, following an insight from Frege, claimed that Emotivism cannot make sense of arguments like the following.

Lying is wrong.
If lying is wrong, then getting your little brother to lie is wrong.
Therefore, getting your little brother to lie is wrong.

Question: What is the problem that Geach and others have highlighted?