For years, Facebook has been in a defensive crouch amid a slew of privacy scandals, antitrust lawsuits and charges that it was letting hate speech and extremism destroy democracy. Early Thursday, though, it abruptly pivoted to take the offensive in Australia, where it lowered the boom on publishers and the government with a sudden decision to block news on its platform across the entire country. That move could easily backfire, given concerns about the company’s influence. But for now it’s a startling reminder of just how much power CEO Mark Zuckerberg can wield at the touch of a figurative button.