Dog aggression towards puppy

Question
Hello!  I have a two year old American Staffordshire Terrier.  I have a question in regards to aggression.  We recently attempted to adopt another female puppy for our home.  She was a mixed breed, (non pitbull) who was 12 weeks old and fixed.  We read numerous articles and tried to introduce the puppy into our home "by the book."  It did not go well.  Our adult dog aggressively attacked this dog on three occasions in about one hour.  Needless to say, we removed the puppy from our home and, thankfully, were able to give her a good home with a dear friend of ours.
I understand that our dog may be dog aggressive.  Although, he has never shown this aggression outside of the home.  I am now worried about him coming into contact with any other dog as well.  My main concern is in regards to whether or not this aggression will also be reflected towards a baby.
A few months ago, a friend of ours stopped over to our house with his baby.  Our dog reacted by barking and growling and then whining incessantly.  I am not planning on have a child for quite some time.  But I am planning on having children during the life span of this dog.  So my question is, are there things that we can do as responsible owners to prepare our pitbull for baby interaction?

Answer
You may have no idea what sort of breeding this dog had, what "lines" he came from, how his parentage was determined; dog to dog aggression can be inherited (and in this breed, unfortunately, THIS IS OFTEN PLANNED.)  Your dog has most likely not been heavily socialized to other dogs; even if he has, he may have inherited a predisposition.  You absolutely cannot bring another dog into your home.  He demonstrated absolutely no warning (according to your description) and obviously intended to kill that puppy.  Outdoors, other dogs are restrained (as is he) and it is not his territory; this does not mean he won't engage another dog physically if given the opportunity.  I can't see that from here.

Regarding your question about infants, your dog has already demonstrated a fear of human infants (as described by you); dogs need to be heavily socialized to everyone: other dogs, children, babies, when they are puppies straight through the second year of life, on a daily basis (or at least four days a week.)  Dogs that do not meet others in this manner can develop fear: in some dogs, this fear results in avoidance, in others it results in aggression.  I CAN'T SEE THAT FROM HERE EITHER.  You need to find a certified applied animal behaviorist to evaluate your dog's temperament and determine whether or not your dog can be socialized to children (which is a VERY difficult thing to do, given that most people are obviously unwilling to offer their babies and children as subjects.)  To find such a specialist, try this link (educational and professional credentials are supposedly corroborated before people are accepted into membership):
http://www.iaabc.org/