HELP ME PLEASE!!!!!!!

Question
Hi Kristin- I hope you can help me in some way, new ideas, or something... so here it goes...

We (bf and I) have 2 dogs both rescue and one is great a little thick headed but great. The other we rescued  
is a 2 year old that we think is a mix between a shepherd and some other random breed.. he was not
spayed when we got him in december but he has been spayed since. It is to my knowledge that he was kept
in a kennel all his life and was never social with other dogs.  He is a wonderful dog inside the house and
just a sweetheart! But as soon as we get him out side and he sees another dog he screams.... and i mean
scream..... he does not bark... it really sounds like a child screaming and once he starts it doesn't stop. We
have tried everything. We have tried tapping him with our foot to grab his attention, we have tried
shhhshing him and lightly pinching him, we have tried flipping him on his back, but it doesn't seem like a
dominance thing, we have tried turning around, nothing works! We have tried a barking collar but since it's
a scream i don't think it is working as it should.

We are a couple that walks them at least once a day for and hour or so each time and at least 3 miles, so
they get exercise, I just don't know what to do any more! I can't give up on him but we have tried
everything. I am afraid to get him closer to other dogs to see if he is curious because there have been 2
incidents that other dogs have broken away from their owners and attacked him.. which he tried to defend
him self. I am willing to get a muzzle to get him closer to other dogs, but we don't know any other dog
owners that would allow us to get close.  Oh... and his attention span is zilch! I believe he was beaten  
before because of his reactions when we move and such.... he has realized that we don't do that but i think
he really might have brain damage... is that far fetched? Any ideas?

I hope you can lead me in the right direction
Thank You for your time and assistance.

Answer
Well what the best idea would be would be for him to meet a smaller calm dog with your dog muzzled,and if you want the other dog muzzled as well so that he can see that not all dogs are going to hurt him-and it would be best to do this with dogs that you know,and you can do with with a few dogs,and slowly get him used to dogs,starting off with something small(even a puppy)and build him up to get used to bigger dogs

I don't think it's brain damage,as brain damaged dogs usually have problems walking,rather then screaming ect What it sounds like is fear,as he has been attacked before and is afraid of getting attacked again

Also you might want to call around to different trainers and see if any are willing to work with him