Awww...he looks so scared in the second pic. I know what you mean though because Peanut is the exact same way. She still gets a little panicky if someone comes in without the doorbell, but not near as bad as if they ring the doorbell. Thankfully, most of our friends know this and don't bother with it - they just walk right in.

I'm no help on the desensitizing thing though. It makes sense that it would work, but I'd hate to traumatize him more if it's not going to work, so I'm just not sure....