We have a farm and we have five dogs that were dropped off and we have taken in. Two of them are pit bulls, the rest are mixed Labs. The Pit Bulls are just as friendly and loving as the Labs, and I have seen no difference in behaviour. And for your information, Collies are considered to be one of the most dangerous breeds, they were not bred to be pets, they were bred to protect sheep, and have one of the highest attack rates.
As far as OP, your anthropocentricism is obvious. Animals are not human, but they are not merely breathing animunculi, and they can think and reason, and they do have emotions. Are they as intelligent as people? No, but I am more intelligent than most people I know, and mentally retarded people are less intelligent than the average. Does that make them of less worth? Because if it does in your mind, you are not someone I would want to share a culture with.