Probably this right here, although I think someone earlier referred to it.
Someone else defended what he said, but there's really no defense. Yes, if someone is knowingly lying about you and passing it off as truth, there is something to be said there (for example, if the Post ran a story "DONALD TRUMP USES MAFIA TO RIG VOTING MACHINES," and the editor had neither a reason to believe this to be true or a source). But Trump specifically takes issue with negative opinion pieces, or even just speculative pieces, and if we start infringing there, we may as well just give up the whole thing altogether. Laws are absolutely fine the way they are right now, and if poor Trumpy doesn't like having his feelings hurt, maybe he should find the social solution of "not making people hate him."