Lesley Stahl, a 60 Minutes news correspondent, once had this interaction with Donald Trump:
“I said, you know that it’s getting tired, why are you doing this (discrediting the media) — you’re doing it over and over and it’s boring,” Stahl said. “He said you know why I do it? I do it to discredit you all and demean you all, so when you write negative stories about me no one will believe you.”
I read that in this Washington Post story, and it’s also available from many other news sources.