I don’t think magazines are ethically required to be open forums for advertisers. Magazines have a symbiotic relationship with advertising because they sell space and make a profit, and in return the ads are seen by the magazine’s readership, but this symbiotic relationship doesn’t require a magazine to accept every or any ad. Magazines have images to maintain. I’m sure Vogue doesn’t want ads for teen retail chains like Factory 4 U. Boy’s Life would shy away from alcohol advertising. Outside magazine probably doesn’t want to advertise Roberto Cavalli stilettos with four inch heels. Ms. Magazine has a feminist, socially just image; if Ms. doesn’t want to accept advertising because they think it detracts from that image, then it is their prerogative to refuse it.
Also, advertising wasn’t paying the bills. At the time of it’s suspension, Ms. Magazine was losing money. If accepting advertising isn’t financially sound, then a business like Ms. Magazine can’t ethically be required to do it.
Magazines are different from Newspapers. They aren’t and shouldn’t be required to be objective; they target specific audiences and promote their own agendas. Magazines are essentially businesses and therefore shouldn’t be required to accept advertising they feel is bad for their business.