You're setting the dog up for failure because you're expecting it to ignore it's instincts and what it's been bred for because that's not what you want in a dog. Whether you train it or not it's a guardian breed and has those instincts, you should have accepted that when you chose the breed instead of just deciding you'll get it PTS if it does what it's been bred for...
I mean lets say a strange man comes to your door at night, you're saying you'd be unhappy if when you went to asnwer it your AB was stood next to you growling at them? Would he be PTS for showing aggression afterwards? How