The swirling debate over how Facebook chooses stories for its trending topics section -- and whether it is muffling stories from politically conservative sources -- refuses to go away, and now the company's leader has spoken up. In a post on Facebook, Mark Zuckerberg revealed that soon he will invite "leading conservatives and people from across the political spectrum" to talk things over. He says the site is building a platform for all ideas, and says the company has found no evidence that an anonymous report of bias in its process is true.