McGahn sees himself as a protector of the "Office of the Presidency"

But not the protector of Trump. Legally speaking this is true. A lawyer in the end in this position has to protect the "Office of the Presidency' instead of the present president or else he puts himself in potential legal jeapordy. This is what happened to John Dean when the president used Dean as a "Fall Guy". At that point Dean realized he wasn't going to take a fall and then co-operated with the special counsel. Until the last few days time for example, most people thought Dean Served time but he says he didn't and instead was in the "Witness protection program" and kept out of sight for his personal protection because the government thought he might be assassinated during the Nixon debacle.