
Done by a knowledgeable breeder, I don't have a problem with it - in fact I have done it myself when I knew not just the parents but generations behind & most brothers & sisters too.
"If the sire has any faults he could of passed them on to his daughter"
Every dog has faults, you just try not to double up on them and looking at it more positively, if both the dog & the bitch excel in some points, these will hopefully come out in the resulting litter.
If it's done without the necessary knowledge then it could be a recipe for disaster. If it's just done for convenience -
it's inexcusable