Issues of going to magazines for current-events aside, I do not understand what your underlying argument is when you say:
how it glibly notes in passing that DJT denies it
If we step away from the context of what happened, are you stating that anything a politician denies must not be true? If you'd like, I'm happy to go into the context of this as well.
I think reputable organizations risk their integrity each time they quote an unnamed source - this is the basis of the public's acceptance of unnamed sourced.
I imagine NBC has a process for using unnamed sources; I know the NYT has one and has written about it in the past.
Thus, I recognize your frustration but do not see the link between 4Chan and a well-known news organization. You might raise the issue of the Vanity Fair reporter's lawsuit, to which I would suggest not reading VF if you no longer believe in their integrity.