It is quite possible that your horse is simply sore from the trim taking off so much all at once causing such a change in the "geometry" of how the hoof impacts the ground that he is now using all of his support system in a different way that causes soreness.
It would be the same to say take a person that wore high heel boots for six months straight and they were running, jogging, walking....basically doing exercise, and every time their foot touched the ground it was in those boots. Now if they were to suddenly switch to a completely flat footed running shoe and they kept with the running, jogging, etc.... they are going to be quite sore because their muscles, tendons, ligaments all have to adjust to the change in one fell swoop.
Truth passes through three stages. First it is ridiculed. Second it is violently opposed. Third it is accepted as self evident.