When I was a child we adopted an abused cocker spaniel who did this aswell and there is no real "cure". It is a life long struggle that he may or may not get over.
We got her at ~2yrs and she piddled every time you said her name/came home/pet her/got the leash/feeding time ect. We had to put her down at ~14yrs and she never fully got over it. (she'd piddle from time to time, but just a few drops instead of a flood)
My advice is just to be as nice as possible and never get angry (walk away if you have to).
A couple things to try:
*Get low, put yourself on or just barely above his level so you're not too intimidating.
*Do NOT stand over him while petting/getting the leash (it's a dominant stance). Instead invite him to you that way he has to approach, you might need treats to lure him in at first.
*Try petting the areas where he's not sensative, work that while relaxing him then slowly and gently pet into the sensative areas. (this should help to de-sensitize those areas, at least with you which is a start)
*CUDDLE: a dog has to trust to be able to cuddle, and more trust in people is exactly what he needs.
*If he's a mischief maker while nobody is home, walk him alot more in the morning. This should help him with pent up energy and then he won't be scared of being told "bad boy" when you get home because he's done nothing wrong.
I'll stand by what wraps said aswell.
good luck and iso pics

e/
no it's not claustrophobia, if anything along those lines he's associated being abused with being at home so he doesn't have an automatic negative association outdoors.
This post was edited by oBlUWUlFo on Oct 22 2015 04:16am