They are irresponsible if they breed their dog to any dog, without doing research on the breed, health certificates, etc.
If they are responsible breeders, they are interested in further advancement of a particular breed, then there is nothing wrong with breeding dogs. However, responsible breeders will not be on YA! looking for mates for their dogs or asking breeding questions - responsible breeders would already know the answers and have mates lined up, as well as buyers for the puppies long before they are even born.