There is a good chance that every dog has been the subject of some sort of abuse at least once in his lifetime. Such abused dogs need special care when it comes to dealing with them. They become uneasy or frightened even in normal situations. Therefore, one must show extreme sensitivity and be very tolerant.
When interacting with an abused dog, make sure you never approach him directly, instead, call him out. Also never talk too loudly at him or around him. Use a calm and friendly tone of voice. And to appear less intimidating to him, lower yourself when you speak to him. Make it a point to show appreciation when he does something good. He might not always do everything right but the trick is to wait till he does. Maybe he is just scared to get too close.