A few stats for you to think about...

You are more likely to get bitten in the US by a Miniature Dachshund than a Pit Bull.

I know someone who runs a shelter in the US and more Golden Retrievers fail his aggression tests that Pit Bulls. GRs are about the most popular breed in the US and are extensively puppy farmed as a result.

Here in Australia you are more likely to get bitten by a Maltese Terrier or a MT cross breed. They are also the most popular breed(s) sold in pet shops and extensively puppy farmed.

Pit Bulls were originally bred to fight other dogs, but to be friendly to humans. Its not in their historical breeding to be aggressive to humans, quite the opposite.

Lots of breeds have a history of being bred for agression to other animals. Pretty much all terrier breeds for example. Jack Russells were bred for killing rats. Dachshunds for killing badgers. All these breeds are more than capable of biting humans.

Many 'pit bull attacks' aren't actually committed by Pit Bulls. One case over here, where a couple of Pit Bulls were identified as the breed of dog responsible for a bad attack, turned out they were labradors. Most people can't identify a pit bull from photos. The media has whipped up a frenzy against a particular breed, as it sells newspapers. Politicians go ahead with breed bans as it pacifies the uneducated public and its cheaper than fixing the actual causes of the issues.

Since they banned Pit Bulls in the UK in the early 90s, the RSPCA estimate that there is now 4x the PB population. Ban something and the wrong type of people want it.

The major problems with dogs in the western world comes from the way we raise them. Puppy Farms produce badly socialised dogs, and badly socialised dogs are ill equipped to deal with our way of life and therefore are much more likely to become aggressive.

If you want a well balanced dog;
- choose a breed that will suit your lifestyle. Getting a border collie without having the time to properly exercise it (body and brain) is only asking for trouble, for example.
- Find a reputable breeder. Meet both the pups parents and decide if they are dogs you like. Talk to other dog owners who have a dog from this breeder. Are they registered with the right kennel club? They should be.
- Never take a dog at less than 8 weeks old. If the breeder offers you the dog at 6 weeks old, they aren't a reputable breeder
- Don't choose the puppy that comes straight up to you, its likely to be dominant. Don't pick the pup cowering in the corner, its likely to be timid. Pick a pup that stays in the midle of the room with the other pups when you go in, but is happy to be picked up and will play with you when you approach it. This pup is likely to be well balanced
- Socialise your puppy! It should meet 100 people and 50 dogs by the time it is 16 weeks old. This is critical!!! Unsocialised dogs are ill equipped to deal with our way of life and this can frequently lead to aggression.

So if I am going on off topic, this is a subject very close to my heart (I work with dogs daily and see the issues first hand. It can be very rewarding but also heart breaking).

Mdinana - your dog sounds like mine. Its partly in the breed, German Shepherds can be bad with other dogs (a lot of solo sheep herding dogs can, animals outside their flock are a potential threat) but I bet its fear based due to poor socialisation. My boy is a rescue Rottweiler X German Shepherd who is beautiful with people / children but a nightmare with other dogs because he has never met them, he sees them as a threat, and because he is usually on a leash outside the house his 'fight or flight' response choice has been reduced to 'fight'. Once he is off leash with other dogs (in a controlled environment) he cowers away. If its causing you issues get in a properly qualified dog behaviorist.