Would depend on the specific situation but the likelihood is your dog is getting put down if it bites someone. Even in cases of self-defence, it happens.
I know, my GSD was trained with assistance from a Police dog trainer, who told me (At the time) what the law was. If you check (and I have) you will find the only legal way a dog can legally bite someone is:
1) If someone breaks into your house (Only house, NOT your garden)
2) If they are a trained security animal, i.e. Police dog
So I'm unsure of your point, because if you take the time to read up you'll see that I agree with you entirely.
Well if a dog has bitten other dogs it is not a big step to bite a human, it happens often.
If you're referring to 'the taste of blood' then it is rumoured that once an animal tastes blood, that's it. I couldn't comment, except to say mine to taste blood as they eat a raw food diet and have done for all their lives.
Also read above, you seem to be missing the point that I agree with you, i.e. if a dog bits a human, generally speaking unless under certain circumstances as mentioned above, they would be destroyed, therefore if as a responsible dog owner, if I believe my GSD is a threat to human life, he would be muzzled. If however a dog attempts to attack him, then said dog would have to contend with me letting my GSD respond, as well as me responding also.
It's only a difficult as you make it.