Conservatives met with Mark Zuckerberg. They still think Facebook is biased.

Facebook's trending news controversy hasn't let up, even after conservatives met with Mark Zuckerberg today. The world's largest social network is still biased, they say, even if that bias sometimes happens unconsciously.

"If you want to be a neutral filter for content — which we think you do — that’s great," said conservative commentator Kristen Soltis Anderson. "But people write code. People are playing a role to fill in the gaps, because AI is not there yet."

The larger issue for Facebook, Anderson said, is the lack of diversity of thought in left-of-center Silicon Valley, whose companies look to attract users of different backgrounds, education and beliefs.

"If there's not ideological diversity — people coming from all walks of life — you may end up with biases you don't know you have," said Anderson, who is a GOP pollster and author of the book "The Selfie Vote."

Anderson was among a group of 16 conservatives who attended a meeting arranged by Joel Kaplan, Facebook's head of global public policy in Washington, D.C., and former member of President George W. Bush's White House Staff who has deep ties to the GOP.

Peter Thiel, a Facebook board member and a delegate for presumptive Republican presidential nominee Donald Trump, joined the session, according to one attendee, along with Barry Bennett, a political strategist who advised Ben Carson's presidential bid and is now a senior adviser to Trump.

Many of those who met Wednesday at Facebook's Menlo Park headquarters are prominent commentators with powerful platforms, such as CNN's S.E. Cupp, Fox News' Tucker Carlson, Dana Perino and Mary Katharine Ham Brewer, The BlazeTV's Glenn Beck, The Washington Times' David Bozell and Jonathan Garthwaite of the Townhall blog.

Others represented conservative organizations, such as former Sen. Jim DeMint and Robert Bluey of the Heritage Foundation, Arthur Brooks of the American Enterprise Institute and Jenny Beth Martin, co-founder and national coordinator of the Tea Party Patriots and a columnist for The Washington Times, and ForAmerica President David Bozell.

Zac Moffatt, who worked as Mitt Romney’s digital director during his 2012 presidential campaign and co-founded Targeted Victory, a company that handles media buying for Republican candidates, agreed with Anderson that anyone who thinks Silicon Valley isn't biased against conservatives "is completely missing the larger picture."

Moffatt was nonetheless encouraged that Zuckerberg took the time to listen to the group's concerns — something that isn't happening at Google or Twitter.

"Not only did he understand our concerns, he acknowledged that Facebook has come up short so far, which I respected," said Moffatt. "But he also said the company would improve."

Moffatt and Anderson are eager to see what concrete steps Facebook now takes to serve users with a variety of views. Facebook acknowledged that it can do a better job of living up to its mission as an impartial platform and a marketplace for ideas, she said.

"This was a great meeting," Moffatt said. "If, in 60 days, we have the same conversation, it was a missed opportunity and a poor use of time."

Zuckerberg issued a public statement that reiterated what Facebook has been saying all week: The social network is a neutral platform for airing "all ideas."

The company is aggressively working to control the reputational damage caused by an anonymous report that it suppresses conservative views for its trending news box — a claim Zuckerberg vigorously denies.

"I know many conservatives don't trust that our platform surfaces content without a political bias," Zuckerberg wrote in a Facebook post. "I wanted to hear their concerns personally and have an open conversation about how we can build trust. I want to do everything I can to make sure our teams uphold the integrity of our products."

A dozen conservatives took part in the hours-long session this afternoon at Facebook's campus, where the company offered a deep dive into the inner workings of its Trending Topics feature.