I'm presuming you mean that these ads are happening in General? If not, I would be very surprised, especially if they are the long and flowery type typically put out by the more literate groups.
If the posts of the people being annoyed are also in General, then...well, there's really not much they can say. If General can't be used for ads, then what are groups meant to do? Run all over the map and spam Local?
Aaaaand if the posts are not in General, then surely you could...ooh, I dunno...turn General off? I dunno.
Not meaning to be nit-picky here, I'm probably just missing something.