I'm with you guys - I distrust dogs who have attacked and feel I'm justified after having been attacked not once but twice in my childhood (I always thought doggies were nice, sweet pooches, I guess).

I have been a volunteer at our local animal shelter and have seen a number of dogs in quarantine due to them attacking or biting someone. Some have been put down while others are released. I'm more inclined to destroy an animal that's either attacked due to instinctive impulse or trained to do so as they may not be trustworthy after an attack and I sure as heck don't trust an owner who either neglects to safeguard others from an unprovoked attack or who may have trained their dog for fighting or to attack. Bad owners are worse than bad dogs in many cases.

Having said that, if a dog defends its owner who they perceive to be needing protection then the owner and hopefully the other party ought to know enough about dogs to understand that they exhibit their loyalty through protecting their master and know how to safeguard the people who approach them and are unknown to the animal.