"Will you acknowledge that you were mistaken in both claims please."

Of course he won't. But then very few of us seem able to do that. Typically we tend to avoid the actual instances where we've been demonstrably wrong and divert the argument to some other safer territory. Time and time again it happens on both sides. ("sides"! That's what happens when discussions are replaced by adversarial contests, arguments or debates.

(Incidentally "I and everyone else knew that" is perfectly correct grammar.)