Rescued Dog and Compassion

Please watch this video.  It is the story of a dog who when rescuers tried to help it snarled and tried to bite.  With patience, the rescuers gained the dogs respect.  The rescuers slowly approached the dog.  Slowly reached to the dog, gradually petted the dog and eventually were able to slide a leash around it's neck. Once in rescuer's arms, the dog feel asleep.
Have you ever met people like this?  When you meet they snap at us with there voice, language and body language.  These are the people we tend to want to leave.  But I wonder if these folks are like the dog in the video.  Maybe they had been treated bad by another, maybe they have had a bad day(s), maybe they never received compassion from another.   Maybe if we approach these people like the rescuers approached the dog, with patience, compassion, and care, we might find they are ok.  Maybe they just need some attention and compassion.  There will always be the people who will always be vicious (like some dogs who cannot be adopted because of biting etc.). This is Ahimsa, one of the Sutras of yoga, non-harming, compassion. 
Do you have any experiences dealing with people who seem vicious?  Please share your experiences and responses.