Large breed dogs can cause a lot of damage.  They can also prevent loss of livestock and personal property. 

A confidant dog can and will protect and or warn people who are crossing the line. Every dog especially dogs that has a guardian temperament will develop a radius.  This will determine in the dogs mind what us too close for their comfort.  If a stranger comes within that radius the dog will respond. We don't know what that radius is.  It's  generally more than our fence line. 

Dogs also communicate using body language.  Two dogs staring one another down is confrontational. Therefore, when a human stares down a dog the dog also should consider this behavior  (body language ) as threatening or confrontational.  The dog can choose to attack or warn with a growl or bark. In most cases a warning will suffice. If the dog's owner is doing the staring the dog should be submissive.  But I don't know why an owner would do the staring. 

This isn't just about confidence.  This is instinctive.  After a dog reaches a certain age these instinctive behaviors should be evident. 

Example : 

We were doing some personal protection training with a group of dogs. There were a variety if breeds and ages.  There was a 6 months old presa. The decoy began shaking a rattle stick . The pup had never seen that before and began to  show protective instincts . This was a good sign. There was a South American Boerboel that was 13 months old. When the rattle stick towards her she didn't show any protective instincts. She was uninterested. The owner of the dog stated that she would respond like that before it was done.  He said it was typical of thus breed that they don't start being interested in doing bite work until they are around 18 months. That is getting more common today for that breed.  That wasn't always the case.