|Just curious, but in the "tests" isn't the dog's pack leader there with him?
Dogs left to themselves make much different choices than dogs who are under the control of their leader.
There is a portion where the dog is tied (to a fence, tree) and a person rides a bicycle, ideally with bells ringing, and any other noise possible, as close as possible by him/her. During this, the handler is not near the dog, but watches from a distance.
Using people milling around, not only in the BH but in other parts of the obedience portion of the sport, the dog may be on but often off-lead and near the handler, yes.
I agree that dogs can make independent choices we may not like (mine counter-surfs when I leave the room) and it is not prudent to leave any dog tied up unattended, for all the reasons PP have mentioned.
However, guide dogs sometimes make independent decisions, (like refusing to step into moving traffic when the owner may be unaware) but you never hear of them randomly biting passerby. Search and rescue dogs are sent independently to find people. Ever hear of a SAR dog, or for that matter, a police patrol dog, biting a child who may well run from it or be afraid of dogs? The dogs used in these types of services are often chosen for their high prey drive. That is a valuable tool to use incentives to train to track, hunt out drugs, be rewarded for making correct decisions.
I agree on the value of teaching children, as much as possible, about careful behavior around dogs and keeping them from approaching strange dogs. What I don't agree is that the OP's child caused the attack, just based on riding by on a bike, because the dog was just a dog and doing what a normal dog would (much less based on prey drive, as I tried to explain in my original post.)
That kind of logic thrown around is what makes it hard for responsible dog owners like myself to rent, get property insurance, have other moms feel comfortable letting their children play with mine, you name it.
I also have zero tolerance for an unprovoked child-biting dog - it is not normal - and like a PP mentioned, if all forbid my dog actually did something like that I would euthanize him in a second, knowing he was NOT being a "normal dog" but had a screw loose and was not right nor safe.
I also highly disagree with the notion that any dog who bites in this particular manner should be rehomed or put in rescue. That is irresponsible on the part of anyone involved, just passing on a problem, and possibly an impending tragedy into unknowing or unprepared hands.