To argue that it applies, certainly. I agree with you on that. But I also wouldn't fault an economist for being unprepared to interrupt or uninterested in interrupting a high-level argument in order to lay the groundwork for the acceptance of that theory (which they presumably have spent some years learning and accepting themselves over the course of their education). One is a conversation about whatever particular situation was being discussed, and the other is a conversation about economics itself; it's reasonable to me that the economist in question could just have been rejecting the change in topic.

But as I commented just now to Vladimir, I was just being wary of a common error which has more to do with social communication than logic; in practice, it does not now appear that the error was committed.