No, journalists are engaged in disseminating the news. They follow the story where it leads. A commentator comments on the new. And a political commentator comments on political news. He doesn't advocate. See how that works?
Think about it in terms of a sports commentator. He does NOT take one team's side in the game. That would make him a fan. And once the sports commentator's objectivity (at least his outward objectivity) is gone regarding everything from whether penalties were committed by one team or another or whether the necessary yardage was gained to achieve a first down, his previous ability to perform his job is gone because his objectivity can no longer be assumed as a given.
I see that YOU refuse to contemplate what "commentary" entails.
If a reporter reports some facts of a story and says "the gas tank exploded" the commentator might add: "and the explosion was fiery and large and loud and hot." He might even say that it was really hot.
On the other hand, he MIGHT just say something like, "and the cause of the fire was found to be negligence and
that kind of negligence is inexcusable." Holy shit. He stated and opinion, but guess what? It's STILL a comment.
See how THAT works?
Edward R. Murrow was a reporter. At some points he crossed over into commentary. For example, in one piece of his famed commentary on McCarthy he asked "Have you no sense of decency, sir, at long last?"
That was political commentary, but if you think it wasn't also advocacy, then I would like to sell you a fine bridge in the Borough of Kings in the City of New York.