Is it obligatory to return the salam to a radio host when hearing it on the radio?

Question:
Your Eminence, a questioner has sent this query: If a radio host greets the listeners, do we return his salam?

Answer:
He does not see you, nor does he intend to address you specifically. This is merely a greeting for the sake of the conversation, and it does not appear to me that one should return it, because he is not intending a specific person. Perhaps no one is listening to him at all; he does not know.