You do kinda have to learn to "speak dog."
I was always a cat guy, and never wanted a dog. I got a 95-lb German shepherd, and all that changed.
I worked through a great book, "How to be Your Dog's Best Friend" by the Monks of New Skete (
http://www.dogsbestfriend.com/books/bk.html ). I learned about training and dogs while he learned how to heel, stay, etc. The level of nonverbal communication you can have with your dog is really amazing.
So anyway, agressive dogs.
You have to first learn to "speak dog" - no way around that. Second, you ABSOLUTELY have to refuse to be number two when relating to a dog. Be nice, and respect their territory (you'd want to bite too if I was rude to you in your house), but don't let them control you. 99% of what dogs do is bluff, to see how you react. They can tell if you aren't going to back down. 99% will back down when they realize you won't. If you do present submission or fear, fewer will back down.
The 1% that will go for it probably won't be prevented anyway.
I'm no expert on fighting dogs, so I won't go there. But that is serious business, so you better be ready to do some damage if you get into it with one.
Scott