invariably makes these discussions fall off a cliff That is of course the political purpose of such remarks. Demonise the other side, brand them as beyond the

invariably makes these discussions fall off a cliff That is of course the political purpose of such remarks. Demonise the other side, brand them as beyond the pale, as not even worthy a reply. This is a well-known rhetorical device to protect one's own position from criticism. Alas it's difficult to defend against.