McNamee is so worried that he wrote a book, Zucked: Waking Up to the Facebook Catastrophe, that debuts on Tuesday. In the book, he details a laundry list of concerns about big tech companies like Facebook and Google, following their many data and privacy scandals and for what McNamee calls their failure to own up to their problems.

McNamee, who has left investing but still owns Facebook shares, says he began his book as a research project in 2016 and then later partnered on it with Tristan Harris, a former Google employee who taught McNamee about how companies leverage psychology to increase use of their technologies. A year later, McNamee was so worked up that he turned from a mere researcher into an activist against the data collection and persuasive techniques that tech companies employ to get people to use their products.

“The problem today is that … the people are not the customers; the people are the fuel,” McNamee said. “We are just a metric. We’re not in any way something they [technology companies] view as human, and that is a huge issue.”

Now McNamee is trying to sound the alarm to as many people as possible about how Facebook and its tech brethren operate—and how consumers can protect themselves.

McNamee talked to Fortune about why he wrote the book and about his experience with Facebook. The responses have been edited for length and clarity:

Fortune: Why write a book now, given your history with Facebook?

McNamee: I’m just a cheerleader, and then all of a sudden in 2016, I started to see things that simply didn’t fit my preconceived notion of the company.

I reached out to Mark and Sheryl [Sandberg, Facebook’s chief operating officer] and said, “Guys, there’s something really wrong here.” What I didn’t realize was how much the culture was a part of that. I was hoping they would take it seriously enough to do internal investigation.

Facebook’s leadership wasn’t interested.

I started researching and met Tristan Harris. When I met him, it was like, “Oh my god.” He’s explaining how Internet platforms use psychology to pray on the weakest aspects of human mind to play on habits and addictions. That’s why the presidential election could be swung, and that’s why the “leave” campaign in Brexit was so much more effective than remain campaign.

The goal was to try to persuade people at Facebook and Google that there was a problem here, and they should fix it. I think it’s safe to say we were unsuccessful in that mission.

What should readers expect from your book?

It’s a narrative, not a business book or tell-all. I use the narrative arch to tell the reader everything they need to know about why I’m an activist and what they can do. It’s about how a toxic mix of uncontrolled capitalism, extraordinary technology, and a culture that says you’re not responsible for the consequences of your actions that can do great harm.

What’s powerful about it is I tell you a lot of things you knew about that you had not connected. Remember, I’m an analyst. My job is to make connections that aren’t obvious, and that’s what I do in the book.

Why do you still own shares in Facebook?

I own shares for a very specific reason. I concluded that I was going to hold my position and ride it out as long as I was an activist. I didn’t want people to think there was some financial motivation. The best way to demonstrate that was to take the same risks Facebook was taking. I wanted to maximize my alignment with the employees.

I think the people at Facebook are good people. I think the combination of the business model, architecture of products, and culture created unintended consequences to well-intended strategies. I can totally imagine how 2016 happened [Facebook’s influence in events like the 2016 presidential election and Brexit] without them being aware. The part that is harder to excuse is the refusal to accept the revelations since and to change the business model-culture arch to protect the people that use the product.

Regardless of Facebook’s scandals, the company’s stock continues to rise. As an investor and now activist, how do you reconcile this?

The world of business has had one rule: The only thing that matters is shareholder value. For a while, there didn’t seem to be downside to that. But now … it’s time to revisit that.

Things are cool … only if you’re shareholder. If you’re a user, things are not cool. Democracy is being threatened by social media. Minds are being messed with.

If we don’t solve this, we’re going to have people with torches and pitchforks knocking the place down.

What was it like serving as a mentor to Mark Zuckerberg?

It was for three years between 2006 and 2009. Zuck had lots of mentors … all more important than I was.

I was brought in to solve a very specific problem. The company was going to be sold to Yahoo for a billion dollars. Everyone around him was telling him to take the money. I helped him get out of it.

That became a very organic relationship. We met monthly for the better part of three years. I really liked interacting with him. If Facebook had sold to Yahoo, we wouldn’t be having this conversation. So I absolutely feel guilty. It’s my job to do what I can to help people see the light.

What was some of the advice you gave him?

I was a facilitator for Mark. I didn’t have any power over him.

Early in our relationship, the issue with the Winklevoss brothers came up [Zuckerberg allegedly stole their ideas to create Facebook]. I helped him get crisis management PR firm to help him learn to deal with legitimate criticism.

I helped him deal with the management team when I first got involved. There was this whole issue of management wanting to sell the company. They weren’t committed to Mark’s mission. So it was about helping him move past those people.

The last thing I did was help him on mobile. His initial instincts were that mobile was kind of a sideshow, and I was pretty confident mobile was going to be the only show. I got to be one of the people to coach him through that.

Do you still talk or maintain a relationship with Zuckerberg?

Hell no. My last communication was Oct. 30, 2016, when I contacted him about the op-ed piece I was going to write [criticizing Facebook]. They both [Zuckerberg and Sandberg] politely and promptly replied. I haven’t heard boo from either one of them since.

Do you think governmental regulation is the solution?

It’s only a partial solution. The point I was trying to make is that humans … have tremendous power—much more power than we realize. But it has to be collectively. If we withdraw a portion of our attention, we can have a really big impact.

Government in Washington, D.C., knows there’s a problem, and they need to know that voters care enough to justify going in and acting. So we also have power to affect political change.

I think we’re going to have to have big changes in how we think data is owned and use, and in antitrust [laws] to create space for new models to come along. This problem can be solved by new businesses.