If the dog is young but aggressive you have an owner problem. So sad for the dog that he ended up where he did, but I would not want to be in a position to not defend myself.
Know the leash laws and aggressive dog laws where you live. Document, document, document. If the owner wouldn't even call the dog they trained to be aggressive, they are scum and the dog will pay the ultimate price for their idiocy.
Thanks!
Ii should also add that I take my 2 dogs to the “doggie park” here in our town every afternoon. There are several pit bulls who come sometimes, and those dogs are very sweet and non-threatening. (I do tend to watch my dogs more carefully when the pits are there, though.)