Do we sin by not returning the greeting to a program presenter on television or radio if he greets?

If the broadcast is live, returning the greeting (رد السلام) is a collective obligation (wajib kifayai), meaning it is lifted from the rest if some individuals perform it. However, it is better for every Muslim who hears it to return the greeting. If the broadcast is recorded, there is no obligation to return the greeting. Some scholars have paused on the obligation to return the greeting if the broadcaster cannot hear the answer, but the precautionary approach is for the listener to return the greeting.