Playing God, even online, is not as easy as it looks. Facebook, Twitter and the other technology firms in control of the social-media universe are learning that with nearly limitless power comes the responsibility to administer it fairly. So far social media has failed. Bias, mostly but not all left-leaning, has obstructed the free flow of dialogue. Unless the tech giants figure out how to remedy their tendency to mediate political discourse by leaning left, the bloom will fade from the unmatched flower of human connectivity, and bad things will follow.