A couple points here. First, thinking more about this, I think the Post has simply made a category error. The paper has a category of news reporters who keep opinion out of their stories. It also has a category of opinion writers who write op-ed columns. It has created a new, third category, bloggers, and it's not clear where they fit. I see Ezra Klein as an opinion writer who does some reporting, and Weigel as a reporter who does some opinionated writing. Holding him to the standards of a straight news reporter seems wrong here. It's as if the Post believes that because Weigel reports, he can't also have opinions -- it's okay to have opinions without reporting, but once you begin reporting then you can no longer have opinions.
Second, Weigel does have a strong reputation on the right for the fairness of his work. Here's National Review's John Miller:
I was startled to read some of what Dave Weigel had written on that listserv—I had taken him to be a left-of-center libertarian, not a cheerleader for Democrats. That's because I knew him primarily from his work. Granted, I'm no expert on his Washington Post blog. I turned to it from time to time, not daily. Yet I found it basically reliable and professional. Perhaps others had different impressions; this was mine. More than anything, his private writings seemed out of character and unrepresentative of his public work.
I had a single direct experience with Weigel. Earlier this year, he interviewed me on one of conservatism's niche subjects and the result was a thoughtful and well-reported piece. There was no bias or unfairness or snarkiness. It was the work of a reporter doing his job.
And here is the American Spectator's Phillip Klein:
This and other private comments by Weigel have contributed to the charge that he's hostile toward conservatives and a standard issue liberal, but I don't think that's accurate. I could just as easily report on private conversations in which he's revealed a fondness for Ronald Reagan, a willingness to vote for Bobby Jindal as president, and agreed that Van Jones should have been fired for his 9/11 trutherism. Plus, it should be noted that in the past, he's even contributed to the American Spectator.
It should also be noted that he went on Keith Olbermann's show and shot down a story about Sarah Palin committing perjury that had been lighting up the liberal blogs and defended Cato's Michael Cannon against a "dishonest and unfair hit" by the Center for American Progress.
I've disagreed with Weigel on a number of occasions, and have called him out when I've felt he's placed an inordinate amount of focus on fringe characters or extreme statements made by conservatives. But I also know that he isn't some "drive by" journalist. He knows his subject matter well, reads constantly, goes to lots of conservative events, maintains friendships with conservatives, and talks to a lot of conservatives for his articles and quotes them accurately.
I can see why the Post would not want a straight news reporter expressing strong political opinions, even in private, or semi-private. But, again, that wasn't Weigel's role. And the irony of the paper's prioritization of the appearance of fairness is to lose a reporter who was unusually good at the substance of it -- probably the Post reporter most respected by the right.