While I do agree with the others that you could have worded things better, I thought I might as well toss my two cents in as well in the off chance you decide to read this.
I am currently also dealing with a buddy sour horse, though she isn't as bad as your guy since I haven't allowed it to progress any further than where she's at now.
What she has been like, is to get all prancy when taken out of the pen and led anywhere else farther off. There were times she'd try to walk or prance past me, especially on the way back. If I was to ride her, she'd back up, turn in sharp circles, canter while only going at the same pace as a fast walk, and so on.
What I have been doing, is working her inside the pasture where she is with her buddies. This way, she's calmer, and is able to focus on me better. This way, I can establish my leadership in a calmer environment. I first started on making sure she listened to any ground work that I asked of her such as back up, leading, flexing, lunging, lowering her head, and so on. Once she was good with this, I tacked her up and worked her with the gear on. Before long, I started to work on riding her in the pen. While she's still throwing her occassional fit, she's improved a great deal as we can walk around calmly now, where is before it was a fight. Her trot is improving as well, but there's still much more that needs to be done and this is with riding her in a halter to get her soft and responsive again.
Between these sessions, I would take her for walks. First they would start off short, but slowly I would lengthen them. And every time she walked calmly next to me, I'd praise her and reward her with pets, or treats to make it as pleasant an experience as possible while away from her buddies. And when she would start to walk past me, I'd do a sharp turn the other direction. After doing this a few times, she's decided it's easier to just walk nicely next to me.
Another thing that really helps when leading them around, that I find, is to talk to them. Tell them your hopes and dreams and positive stuff that makes you happy as they will pick up on your good relaxed mood and it will help them to calm down and feel relaxed with you. With my mare, we are now able to go for calm walks a long ways off from her buddies without her getting worried or doing any prancing, and her riding is coming along as well. It's a long process, but very rewarding in the end.
Hope you manage to find something useful in this and what everyone else has posted as it's all very valuable stuff to know, as everyone here is just trying to help you.