This week, a number of companies pulled their ads from Bill O’Reilly’s Fox News show after the Times reported that the host and his employer have paid millions of dollars to settle accusations of sexual harassment and other inappropriate behavior by O’Reilly. Angelo Carusone took the opportunity to begin tweeting from an account that he set up in March, 2010: @stoporeilly. In 2009, Carusone’s @stopbeck account pressured brands to pull ads from the program that Glenn Beck, the conspiracy-minded conservative commentator, was then hosting on Fox News. It proved an effective tactic. Partly in response to Carusone’s tweets, advertisers began to disassociate themselves from Beck’s show. Beck and Fox News parted ways in 2011. Carusone started working at Media Matters, the left-wing nonprofit that battles what it considers “conservative misinformation” in the media, in 2010. He’s now the president of the organization. On Tuesday, Carusone spoke by phone about his Beck campaign in light of the ongoing O’Reilly situation. His account has been edited and condensed.

“Leading up to the summer of 2009, I was a second-year law student. And when you’re a second-year law student in springtime, procrastination becomes something you look for. That was right at the same time that Glenn Beck was on the rise. He was something different for Fox News. It’s not that he was ideologically different, but his presentation, his manner—it was much more venomous and vitriolic than even the standard Fox News fare. And he was incredibly successful by all measures, in audience size and revenue, and the kinds of advertisers he was attracting.

“My fear became that the market would actually create an environment where people who were doing what Glenn Beck was doing became the new norm, when they should be anathema. That’s what planted a seed in my brain. Twitter had finally become more of a thing. You could access companies in a different way, because your communications were very public and transparent. I started the Stop Beck campaign right at the beginning of July, saying, I’m just going to contact advertisers and say, ‘Hey, this is what Glenn Beck said today. This is what your ads are appearing next to.’ So that they would be able to see the association, what they were actually paying for.

“That’s how it started. I listened to his program every day, tweeted everything he was saying, copied in the sponsors. At the end of that month, Glenn Beck called President Obama a racist and said that he had a deep-seated hatred of white people and white culture. That caused a firestorm. Big organizations got involved, which was something I’d never even conceived of. I was a Twitter guy. Color of Change and some other activists groups sent out petitions. I got a ton of new followers and new participants in my effort. And then all of a sudden I had a blog. And Kraft, the cheese company, replied to one my blog posts saying, ‘Hey, we’re pulling our ads from Glenn Beck’s show.’ Literally in a comment. That’s how it started for me.

“About three months in, I was, like, O.K., now I have a theory—but I needed a strategy. What is the actual strategy for holding him accountable? Because, clearly, he was not off the air. You think if you get X number of big companies to leave that it’s just magic—he goes away. I needed something bigger. So what I actually started to do: There was a guy in the U.K.—Glenn Beck’s show was simulcast there—he would watch the show and give me advertiser lists, and some of them were big companies that weren’t advertising here. If you could get their U.K. division to say they would pull their ads, it would filter over to the States. It became a shot in the arm for the campaign. Within a few months, every single advertiser on Glenn Beck’s show in the U.K. had been completely cut off—he didn’t have any more ads. They would just go to essentially dead air, they would just run promos for BSkyB and Fox News during the commercial breaks. No ads at all.

“What I wanted to do was make sure that there was enough of an effect, so that, if Glenn Beck was still on the air, during the next shareholder conversation, Rupert Murdoch or whoever—Chase Carey, who was the C.O.O. at the time—would have to say that there was a problem. I thought, that would finally be the validation that I would need from the business community that Glenn Beck is actually bad for business. They would have to say we have a problem.

“After I came to Media Matters, I was able to quantify the reduction in his ad rates. When you create critical mass, even if other ads are still running, they just won’t pay the same rates. Bill O’Reilly is the Fox News standard-bearer, he’s still their highest rated program, their most valuable asset from an advertising-and-revenue perspective. An advertiser that’s going to stay is not going to pay the same, they’re just not going to do it. At worst, even if Bill O’Reilly stays on the air until he’s ready to leave, his advertising rates will diminish. And the more advertisers that leave, the more that will be affected. It’s market forces.”