When you “buy” a dog, people interpret that to mean that you went to a breeder and purchased a puppy, rather than “adopting” a dog from a shelter that was at risk of being put down. “Buying” a dog in the eyes of some people is supporting breeding, which they consider unethical and wasteful when “there are so many animals that already need homes!!”
The whole thing is just stupid. If someone wants a specific breed, they should be able to get a puppy of that breed without judgement. If you care about the dogs who need a home, go adopt one and stop caring so much about your neighbors animal preferences.