The main reason that dogs are produced from parents with good bites with poor ones is because someone did use dogs with poor bites back in the lines and it Will always out in the end.

there is no reason to use a dog with such a fault when there are exceptional dogs that do not have this fault that could be used instead. That is what selective breeding is about increasing the probability of getting the desired characteristics not taking unnecessary risks of producing faults.

The only justification for using a dog with such a fault would be if he was so outstanding, the last of his line without the benefit of his genes the breed would loose something vitally important. Then the breeders will have to work hard to eradicate the fault when it next appears.

Better not to introduce it into your lines (or double up on it for all you know it could be there already).

The greatest authority on the Bullterrier is largely agreed to be a Mr Raymond H. Oppenheimer.

Here are some of his comments on breeding on a Friends website: Aritaur Dobermanns - Breeding he is quoted about half way down the page.

The first two points I think make things clear:
Raymond H. Oppenheimer wrote:
1. Remember that the animals you select for breeding today will have an impact on the breed for many years to come. Keep that thought firmly in mind when you choose breeding stock.
2. You can choose only two individuals per generation. Choose only the best, because you will have to wait for another generation to improve what you start with. Breed only if you expect the progeny to be better than both parents.