Just in case my post isn't clear, I'm writing about the macro issue that asks, "Is a magazine ethically required to be an open forum for all advertisers who have the ability to pay? According to what standards?"
I definitely don't think a magazine is required to publish all ads that can be paid for. A magazine is not a public forum- magazines have narrow audiences, and the ads within them are specifically for those audiences. If a magazine, let's say one for teenage girls, has stories promoting not drinking, the magazine would be opposing its own information if it published an ad for alcohol. Editors have the discretion to choose which ads will and will not be included in their publications. The same is law for newspapers- editors decide. If the magazine loses readers because of the narrowness of ads, then perhaps the editors can choose to include more. However, I'd think that they would be more likely to lose readers by having ads the audience isn't interested in.