You, sir, are absolutely correct.
Had this hit piece been directed towards any other citizen other than the President, CBS/Rather et al could have been sued for liable and slander, and would have lost big time $$$$. It is only because the presidential seat carries with it a, shall we say, "responsibility" that it must endure being relentlessly attacked, rather [no pun intended] than being the attacker, that such a lawsuit never happened.