Guilt-tripping that people should only ever get rescue dogs really is attacking the problem from the wrong end.
When 'demand' for puppies in a certain breed dries up, who do you think will avoid having a litter - the responsible breeder, or the puppy farmer who sees the dogs as commodities and washes their hands of them as soon as they leave the premises? It is not the responsible breeders we need to stop, it is the others, or we will be left with a population of dogs bred with no care for health or temperament (or breed type, although I appreciate that isn't important for many people).
Rescues are not generally full of dogs from responsible breeders - I am not saying it never happens, and when it does it is generally because the owner feels guilty for having let a responsible breeder down or doesn't think that the breeder who promised a lifetime commitment to their dogs actually meant it - believe me, many do! I have seen breeders move heaven and earth to try and help their dogs if they do end up in this unfortunate situation (often met with stonewalling from charities, with their bank balance in mind rather than the welfare of the dog).
I don't know what the answer is, really. Education clearly isn't working, there is no excuse at all for anyone not to know about the horror of puppy farms - and it is not just idiots buying there either, I am amazed at some of the people who wilfully ignore the situation to get that cute puppy.
That said, I don't fundamentally have an issue with anyone advertising on these sites when they are vetting homes properly, for the odd puppy that wasn't pre-booked, a larger than expected litter, a sale that has fallen through, etc.
Better that there are some quality adverts on there, listing the results of health tests that should be taken - perhaps then at least a few people might realise there is a difference. Price is usually the same too, and quite often lower.