Six year old gelding, turned aggressive after lunging?

It really sounds like someone hurt him in the past with a lunge line, whip, or something with lunging. First off most horses who have no idea how to lunge can be afraid of the rope, I would try free lunging him. I know all the ones I have trained feel much more at ease when they don't have someone holding them back. Also always give a treat for when he does even a little bit of good. It does sound like he might be playing you this sounds mean but next time if he runs at you pop him with the whip even if it is his face. He will soon learn that this is a bad thing to do. Don't worry about hurting him, I mean don't beat him just a pop.