He is absolutely correct. MAD is for deterrence. If your enemy already launched the missiles, there is no point in killing millions just for revenge. Obviously

He is absolutely correct. MAD is for deterrence. If your enemy already launched the missiles, there is no point in killing millions just for revenge. Obviously, you cannot have this benevolent mindset in the first place, because your enemy will know he can destroy you without consequences and thus won’t be very much deterred from it. Even the name MAD was a reminder to the other country that the US was indeed crazy enough to destroy and kill millions if USSR attacked.