I’m not saying to turn the other cheek and always say something polite as a general principle; by all means lash out at your critics, if you have something to gain by doing so. Rudeness at the proper moment can serve a purpose — as I hope I’ve demonstrated over the years. But if you vent for the sake of venting; if you alienate people you’re going to need; then you’re just being stupid.
And that, I’m afraid, is what’s going on here. Rachel Maddow isn’t going to go away, or turn all meek, because the White House Press Secretary implicitly denounced her. Even more to the point, liberal critics have an audience because they’re reflecting real concerns of real people. Those concerns need addressing, if necessary in the form of explanations of why their expectations can’t be met. Denouncing the people giving voice to those real concerns as the “professional left” is both unfair and, as I’ve said, stupid.