Just like the writer said, that only hurts CNN. They've basically backed themselves into a corner. Trump has nothing to lose. Their coverage of him is already wall to wall negative as is. If Trump fires back what are they going to do? Get even more negative?
Then, as the writer said, Trump can spin it on them and point to the fact that they dislike him, warned and threatened him about doing this very thing, and say that they're nothing but opinionated, hack journalists out for revenge because he didn't heed their warning or cower to their threats.