The joke was that Obama wasn’t joking
There are no jokes there. There’s just Obama saying what he has to say and Luther saying what Obama actually believes.
And what Obama believes is that the press is often sensational, trivial, and fearmongering. He thinks they hype negative stories for weeks on end and then refuse to admit their mistake when the horror fizzles. He thinks he gets the blame for catastrophes but little credit for solutions. He thinks the media has a deep bias toward negative stories (which, of course, we do).