Trump has never acknowledged Russian interference in our elections, which is a GIVEN FACT in the Mueller report. Now comes the news that Nielsen was actually concerned about it, but told not to discuss the issue with Trump, for fear it would send him off the rails.
So the President, when faced with concrete evidence of a foreign power interfering in our political process, does what? Nothing.
"I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States."
Somehow, I do think that he's missing the mark, on that oath he took. And Laurence Tribe feels so too.