Honestly, news organizations should just double down on criticizing Trump. What is he gonna do? Ban them all until he sits there alone with Fox News and a couple of right-wing bloggers? If that happens, and Fox News is suddenly the most reputable news organization in the room, I conjecture that even they would eventually clash with Trump over something, at which point even the dumbest of his supporters will have to realize that the problem isn't the news organizations but Trump's pathetic little ego.
Edit: I may be underestimating how dumb some of his supporters are, but here goes my half-baked take.