
Taking him out for a walk while he is this scared is only going to make him more frightened, he won't be able to trust you if you insist he goes for a scarey walk or even if you insist he follow you to the front door (this is not having a go at you, it's more of 'from the dogs point of view')
I had this problem with my pup, he was used to the lead in the house & garden but was frightened to go out for a 'proper' walk. He would happily have his lead on unless I was headng down the hall to the front door, he would then freak out.
I used to go and sit inside by the front door (with it shut), if pup showed any interest in me (looked in my direction) I would chuck a treat to him. This progresed to him being brave enough to sit by the door with me.
I then introduced the lead and would have it clipped to pup's collar while we sat by the door, when he was comfortable with that we would sit inside with the door opn, all the while lots of treats and praise for any signs of interest in outside (eg. curious sniffing).
We then would sit outside the door for about 30 mins twice aday, just sat on my front lawn so pup could get used to the sights, sounds and smells of the big wide world, again, lots of treats and praise.
After what must have been a few weeks, we actually went for a walk - a few yards down the road and strait home. Gradually the distance was increased and now at 15 months old my dog LOVES going for a walk, occasionally he'll see something that will make him a little nervous, but I've sussed out how to give him confidence. He saw 2 traffic cones stuck in the middle of the path (in a field) and started to spook, I let his lead out longer (long-line) so he could retreat if he wanted while I walked up to the traffic cones, coupied down, stroked the cones and had a happy little chat to them - I must have looked like a complete wierdo but it showed my dog that I thought they were friends, now when he see's traffic cones he like to go & greet them!
I found that too much verbal encouragement (ie, 'come see', 'what's this') was just too much pressure for pup and would help to freak him out, it worked better for us if I kept my mouth shut untill he did somthing that warrented praise (step towards door, curious sniffing etc..).
As well as being frightened by going for a walk, this is something he has done for years so has conditioned himself to act like this and turn it into a habbit, he needs a lot of work to help him get over this. I think a behaviourist would be the best bet.