You are using human ideas of incest and applying it to animals. When we SELECT for vigor and fertility, as well as for other attributes, there will be less talk about the evils of inbreeding. In the meantime we shall hear about it mostly where vitality and fertility were low in the stock inbred upon. Because both of these are requisites - one to insure life and the other for reproduction-they should be possessed in a high degree by the dogs one intends to inbreed upon. If no other animals are related, but one animal is related on both sides, we breed in-line to that animal. All the "pulls' are in the right direction and we double up allele pairs that we like!