5) The media is a political actor, not an observer.
It seems to me that the useful thing to know about the media has to do with media biases. Americans overwhelmingly believe that the press has a liberal bias, but that's because Republicans have used it as a talking point for forty years. In fact, while it's true that reporters are overwhelmingly liberal, it turns out that studies looking for liberal (or conservative) bias mostly turn up nothing. Now, one has to be careful defining terms here. If one believes that gays and lesbians are deviants, then one will judge it media bias if gays and lesbians are treated as normal, ordinary Americans. If one believes that capitalism is evil, then one will judge it media bias if capitalism is treated as normal, or even as good. What the media bias studies show isn't that there's no (ideological) bias; it's just that the media tend to treat as normal things that most Americans view as normal. Sometimes, what most Americans believe is wrong or goofy, and in those cases the press will tend to reflect the beliefs of most Americans, for better or worse. There are some exceptions to that generalization, but overall it's probably pretty accurate.
That doesn't mean that the press isn't biased. In fact, researchers have found lots of biases, but they tend to run along the lines of two things: biases in the press's self interest (they like things that sell more papers or get higher ratings), and biases produced by the way that reporters do their jobs. The first part of produces things like a tendency to feature sex and violence, a tendency to prefer good stories to important stories, and a tendency to personalize things (which also yields the tendency to focus on presidents and not Congress, since the former is less abstract). The second part produces things such as pack journalism, an emphasis on breaking stories, and far more coverage of those things with established beats (and areas with news bureaus) than those things and places without those advantages.
All of that is about the "objective" press -- not that it's perfectly objective, but that it strives to be neutral between political actors. In the heyday of the objective press in the middle of the twentieth century, the paragraph above would cover most everything but a handful of tiny, mostly inconsequential magazines and a handful of op-ed columnists. Obviously, the world has changed and is changing, and we don't know yet what will come out the other side. What it looks like so far is the revival of a partisan press, which includes things such as Fox News, the prime time talk shows at MSNBC, and on-line sites such as Josh Marshall's Talking Points Memo. These outlets are clearly biased in favor of a party or an ideology, and in fact are probably best thought of as part of their party networks.
Back to Ezra: he's absolutely right that reporters are political actors, whether they are part of the nineteenth century partisan press, the twenty century objective press, or today's mixed group.