I don't breed them for other people I breed them for myself. I wouldn't come to you for a purebred dog anyways, I'm quite happy with my purebred miniature dachshunds.
I don't think Oregon Blues was implying that you would be breeding for others, or that you would actually come to them for a purebred dog. The point was that breeding chickens (and many other livestock species) is a lot different from breeding dogs or other companion animals. With companion animals, a breeder has a responsibility to know exactly what will happen to each animal they produce and to know what the buyer's plans for that animal are. With chickens, there is a lot less of a vested interest. Sure, you will have some breeders who only want their birds to go to other breeders who are striving to improve, or at least maintain, the breed. But for many, probably most, once the bird has left their property it is no longer their concern what the buyer plans to do with it. If they don't want their birds going to produce inferior or mixed breed chickens, then they simply don't sell them. There are many breeders who are working on project colors or breeds that kill every single one of their culls because they don't want poor quality birds running around out there with people claiming that they are their (the original breeder's) lines. Instead, to ensure that they maintain their reputation as producers of very high quality birds, they wait until they are satisfied with their projects before they offer them for sale. Some serious breeders working on project birds that don't want poor examples of the birds they are working on running around with their name on them will also cart them off to a local auction where no one is really that into breeding and showing and no one knows who's birds they are.
From what I can tell, most breeders that won't sell only pullets/hens and only sell birds as pairs or trios are doing so more because they have a need to get rid of roosters they don't want/need in their own breeding program than because they actually want the buyer to continue breeding the birds. The demand for pullets always far exceeds the demand for cockerels, so selling them as a pair or trio is one way to make sure that the boys sell too. It's not that they will be mad if you don't breed their birds, or if their birds go on to produce mixed breed chickens, but rather a convenient way of getting rid of extra boys.