On what grounds can FIFA interfere here?
The journalists are free to sue Diego and only the court can punish him if he's found guilty. FIFA can not punish him.
It would've been different if he said that to the referee during a match, but how on earth can FIFA punish him for insulting the journalists?
If Maradona makes a video where he tells his wife "Suck my dick" and if it goes public, can FIFA punish him for that? It's the same case with the journalists.