When you write for a magazine with a particular ideological bent, it's natural to wonder whether you're being too soft on "your" side. This question comes up more when your side is in power, since they're the ones who are implementing policies and making decisions; when the other side is in charge, most of your time is spent documenting and analyzing all the harmful and dangerous things they're doing, and your side is occupied with fighting the ruling party and waiting for its turn. Obviously, politics is a neverending conflict, and that conflict can produce a certain siege mentality. For instance, when a Democratic president proposes a plan for universal health coverage and Republicans attack it with a campaign of mind-boggling hysteria and dishonesty (death panels!), it's natural to spend a good deal of time correcting the record and defending it, even if you think that plan is less than ideal. There are some people (like Glenn Greenwald) who write largely about one set of issues, and thus may find themselves regularly criticizing a president from the party they're closer to if that party doesn't live up to the standards they hold, but if you write about a range of issues, most of the time you won't be critical of your side for the simple reason that most of the time you agree with what they're doing.
That doesn't mean that by doing so you've abandoned critical thinking. On health care, for instance, my own position was like that of many liberals who wrote a lot about the issue—that the Affordable Care Act had a number of weaknesses and could have been much better than it was, but nevertheless represented an extraordinary advance that would have a positive impact on millions of lives. Did the second part of that position make us unthinking water-carriers? I don't think so, but Matt Welch of Reason might argue that it does. In an article titled "The Death of Contrarianism," Welch laments that while liberals (and liberal magazines) used to be skeptical of liberalism, in the Obama years they've become little more than a bunch of Democratic party apparatchiks. "The reformist urge to cross-examine Democratic policy ideas," he writes, "has fizzled out precisely at the time when those ideas are both ascendant and as questionable as ever." Welch seems to pine for the time when The New Republic was torpedoing Bill Clinton's attempt at health care reform by publishing the policy con artist Betsy McCaughey and beating the drums for the invasion of Iraq, because that represented a healthy contrarianism.
You should read Ed Kilgore's response to Welch, but I'd point out that contrarianism in and of itself is nothing to be proud of. It can be as thoughtless and as indiscriminate as dogmatism. There's no inherent value to arguing against the prevailing wisdom on your side of the debate unless that wisdom happens to be wrong. I could boldly claim that Wall Street executives are underpaid and should be allowed to pay a zero percent tax rate on their income, and liberals would disagree. But their disagreement wouldn't make my argument more persuasive, or make me more of an independent thinker. When The New Republic tried to convince its readers that invading Iraq was a splendid idea, they were certainly running against the prevailing tide on the left. But as it turned out, they were horribly, dreadfully wrong. Their contrarianism did nothing to redeem their mistake.
Nobody likes to think of themselves as a mindless partisan, even people whose job it is to be partisan. This reminds me of a line I read this morning in a New York Times article about Lindsay Graham, a generous profile in which Graham is portrayed as bravely seeking compromise on immigration in the face of the doubts of his constituents. The piece observes that Graham has used his Benghazi crusade as a way to bank goodwill on the right, then includes this laugher of a sentence: "'Anytime you challenge the president, Obama, it's good politics,' [Graham] added, but pointed out that he was equally critical of President George W. Bush on foreign policy." The reporter did not note whether she did a spit take when Graham said that he was just as critical of Bush as he has been of Obama, but if the Senator believes that, I would recommend that he immediately consult a neurologist to determine the source of his memory lapses. So why did Graham feel the need to say this? Because even one of the most conservative Republicans in the Senate likes to think (and have other people think) that he's an independent soul who won't hesitate to attack a president from his party. That happens not be true in his case, but he still wants to believe it.
If you're going to say that liberals should be questioning Democratic policies more, you have to be specific about what they should be questioning. Welch only cites two policies he thinks liberals should reject: a higher minimum wage and universal pre-K. But guess what: liberals think those are good things! I suppose we could bash them, just for the sake of being contrarian. But what would be the point?