Rush Limbaugh’s opponents were starting a radio campaign against him Thursday, seizing upon the radio star’s attack of a Georgetown law student as a “slut” to make a long-term effort aimed at weakening his business. The liberal Media Matters for America is using a past campaign against Glenn Beck as a template. In Limbaugh, however, they’re going after bigger game. He’s already fighting back and the group’s stance has provoked concerns that an effort to silence someone for objectionable talk is in itself objectionable. Media Matters is spending at least $100,000 for two advertisements that will run in eight cities. The ads use Limbaugh’s own words about student Sandra Fluke, who told congressional Democrats that contraception should be paid for in health plans. Limbaugh, on his radio programs, suggested Fluke wanted to be paid to have sex, which made her a “slut” and a “prostitute.” In return for the money, he said, Fluke should post videos of herself having sex. Under sharp criticism, Limbaugh later apologized. In one of the anti-Limbaugh ads, listeners are urged to call the local station that carries Limbaugh to say “we don’t talk to women like that” in our city. Ad time was purchased in Boston; Chicago; Detroit; Seattle; Milwaukee; St. Louis; Macon, Ga.; and Cedar Rapids, Iowa. A spokeswoman for Premiere Radio Networks, which syndicates Limbaugh’s show to nearly 600 radio stations nationally, said Media Matters has gone beyond criticism of Limbaugh’s words to an attempt to silence him and intimidate advertisers. Radio stations in Hawaii and Massachusetts have dropped his show. Media Matters claims that 58 companies have specifically asked that their ads be excluded from Limbaugh’s show. Radio-Info.com’s TRI Newsletter said a group with several stations that air Limbaugh sent out a list of 31 advertisers who don’t want to be on Limbaugh’s show.