On Monday, the Associated Press reported that Twitter had staged an intervention in America’s political discourse, but one that had nothing to do with the Russian bots that you’ve heard so much about:Republican Rep. Marsha Blackburn’s Senate campaign announcement ad has been blocked by Twitter over a statement the abortion rights opponent makes about the sale of fetal tissue for medical research.\n\n\n\nBlackburn, who is running for the seat being opened by the retirement of Tennessee Sen. Bob Corker, boasts in the ad that she “stopped the sale of baby body parts.” A Twitter representative told the candidate’s vendors on Monday that the statement was “deemed an inflammatory statement that is likely to evoke a strong negative reaction.”As a result, the platform rejected Blackburn’s ad and refused to promote it. Meanwhile, that very same day, white supremacists, alt-right bigots, and other malignant conspiracy theorists ran rampant on the platform, as they do every day. Here is former KKK Grand Wizard David Duke claiming “Zionist neocons” (code for “Jews”) support ISIS:Here is notorious misogynist, rape apologist, and Pizzagate promoter Mike Cernovich bragging about his Twitter traffic:And earlier this week, here is white nationalist darling Richard Spencer retweeting Kevin MacDonald, “the neo-Nazi movement’s favorite academic,” thanks to his authorship of “a trilogy that supposedly ‘proves’ that Jews are genetically driven to destroy Western societies”:Should Twitter be censoring these users and their malicious falsehoods? Or should it desist out of a concern for free speech, and let good ideas rebut bad ones in the public square? The problem is not that Twitter chose one of these options and not the other. It’s that it chose both. In censoring Blackburn but not Duke and the alt-right, the company demonstrated a selective standard for free speech—one that should disturb all Twitter users, no matter their politics.After all, what rationale is there for blocking Blackburn’s anti-abortion assertions but not far uglier racist conspiracy theories about Jews, African-Americans, and others? Some might argue that the difference is that Blackburn sought to turn her video into a promoted tweet, while Duke and Spencer have simply used regular non-promoted tweets. But if the content of an ad is truly too inflammatory, why is that substance suddenly deemed kosher when it is packaged as a plain tweet? If Blackburn’s controversial claims about Planned Parenthood’s treatment of fetal parts is fake news, why isn’t David Duke’s ranting about Jewish control of the media?When faced with questions about bigoted and abusive users, Twitter has often defaulted to its commitment to free speech in its defense. When in doubt, err on the side of open discourse, the company has argued. Yet Twitter’s conduct toward Blackburn, a sitting U.S. congresswoman, shows that the service is perfectly willing to set aside such scruples when it feels so inclined. Why, then, did Twitter allow Cernovich to use its live-streaming video service Periscope to slander an innocent man as a Pizzagate pedophile?I've been relentlessly libeled by Mike @Cernovich. He claims I'm the leader of a child sex ring on @Twitter. @Jack, PLEASE stop his abuse. pic.twitter.com/HelBSzTlOD\n\n\n\n— Vic Berger IV (@VicBergerIV) December 19, 2016Twitter’s non-transparent and unbalanced standards for acceptable speech are further evidence that the public should be skeptical about empowering giant social media corporations to police what can and cannot be said on the internet. These companies were built to make profits, not serve the public interest. Since the 2016 campaign, expecting them to accurately identify misinformation and abusive content has led to false positives and often abject failure. Whether their choice is a free speech free-for-all or careful curation, these services much be consistent and transparent in applying their standards. Twitter, Facebook, and Google can and must do better, and they must do so in public—or be held accountable by the public.