They're really not. Anyone who pays the owner money can advertise whatever they want.
If you can show some credible evidence that they don't follow their own guidelines for what's an acceptable ad, which seemingly restricts what advertisers can push out, then "advertise whatever they want" is a bit sweeping.
I'm in two minds about the Acceptable Ads feature in Adblockplus. On the one hand, it's giving in somewhat to advertisers, but on the other hand, it's arguable that it encourages/pushes advertisers to limit their excesses, which is itself a good thing. I use Adlbockplus myself, but I do turn off the Acceptable Ads feature (personally got fed up with the excesses of the advertisers over the years, so decided to burn all their houses). Still, as long as I can disable the feature, and Adblockplus still blocks ads, then I'm fine with it as an interesting compromise (for others to try out