what about going slowly and introducing him to other stuff related to dogs (but not actually a dog)

what i mean... i remember seeing a programme on TV where people were trying to cure their animal phobias (it could be dogs, birds, what ever)

what they did is first show that person a picture of that animal (nothing more, just a picture), then a video of that animal, and then they'd slowly introduce the person to the actual animal.. so if the fear was say, horses, they'd go to a stable and watch horses over the fence until that person felt they could actually go and be up close to them

so what i'm saying is.. if you show him a picture of a nice dog, a video of a nice dog, and then try to find 1 (but don't actually get too close at first), it might work