that's almost sick! yes, a lot of adult dogs do get PTS every year by shelters. so do puppies. just because the puppy has not had the chance at a life doesn't mean it is "less" than the adult dogs. shelters give the adoptee plenty of choices to find the right dog. homeless puppies should be treated the same as homeless dogs.
Of course the puppies are not "less" than the adult dogs. However they would suffer "less" if euthanized at birth than an older dog that has already known love and been abandoned only to die alone and unloved in a shelter environment.