"The reason I care so much about this is that it gets to the core of everything Facebook is and everything I want it to be," Zuckerberg wrote in a post on his Facebook page. "Every tool we build is designed to give more people a voice and bring our global community together. For as long as I'm leading this company this will always be our mission."
In the same post, Zuckerberg said in the coming weeks he will invite "leading conservatives, and people from across the political spectrum," to talk with him about the allegations.
The issue got heated earlier this week after tech blog Gizmodo, citing anonymous sources, reported that Facebook workers routinely kept stories with a conservative bent out of the Trending Topics list and injected stories that weren't as popular.
The issue cause enough of an uproar that U.S. Sen. John Thune (R-S.D.), chairman of the Senate Committee on Commerce, Science, and Transportation, sent an open letter to Zuckerberg, asking him to answer questions about the allegations.
"To serve our diverse community, we are committed to building a platform for all ideas," Zuckerberg wrote on Thursday. "We take this report very seriously and are conducting a full investigation to ensure our teams upheld the integrity of this product. We have found no evidence that this report is true."
Zuckerberg was smart to address the issue head on, said Zeus Kerravala, an analyst with ZK Research.
When the issue first popped up, Zuckerberg was silent, while Tom Stocky, Facebook's vice president, search, and a member of Facebook's Trending Topics team, commented on it in a post on his Facebook page.
At the time, some industry analysts said that wasn't enough and Zuckerberg himself needed to get involved.
"Now they've done all you can ask," said Kerravala. "They addressed it and published the policy. And no one has proof they aren't following the policy."
On Thursday, Justin Osofsky, vice president, Global Operations, at Facebook, also posted a statement on the company's media page.
"The guidelines demonstrate that we have a series of checks and balances in place to help surface the most important popular stories, regardless of where they fall on the ideological spectrum," he wrote. "Facebook does not allow or advise our reviewers to discriminate against sources of any political origin, period."
He then provided an overview of Trending Topics, which was first added to Facebook in 2014, and the guidelines that members of the Trending team are given to follow.
Osofsky also said topics are not blacklisted.
"The guidelines do not permit the suppression of political perspectives," he wrote. "About 40% of the topics in the queue get rejected by the reviewers because they reflect what is considered "noise" -- a random word or name that lots of people are using in lots of different ways. For example, braised, DVD, #weekend and #sale are all topics that were not accepted as trends over the past week."
Osofsky added that Facebook is continuing to investigate the allegations.