My white german shepherd..3 yrs. old is no watchdog

Question
I got him at a shelter a year ago.  He is aggressive with dogs..He was obedience trained when I got him.  But any stranger can enter ..with or without me there and he does not bark.  He would help them carry the furniture out.
He is 110 lbs. pure white.  Great with people. He is altered.  Can a shepherd not be a watchdog?

Answer
Yes.  I have often said dogs don't read breed descriptions and fail to live up to them. Some of my Labs hate the water.  One of them ate like a Shepherd, even on a concentrated chow, his ribs showed.  Many people would trade dogs with you in a heart beat.  

If you would like a little more warning when people come around, perhaps arrange with somebody he doesn't know come to the house and holler and scream at them, praising him if he starts barking.