Just out of curiosity, have you tried a different vet? (assuming there is another good one semi-locally) We have one horse who had a MAJOR injury and was treated by the best vet in the area several years ago. To this day, if that vet shows up to do ANYTHING the horse turns into a raving lunatic (though he doesn't drag anyone, just dances like a fool). I can give him shots and he doesn't flinch, but the vet approaches and its like he thinks he's going to die! The vet, of course, understands the situation and handles it very well, but it is beyond irritating! If your horse has been treated for something painful by that vet, it would be understandable (but not acceptable) for him to react badly to the vet's presence. Also, is there any chance that your vet is under-sedating?
A horse that's properly sedated really shouldn't be dragging you anywhere. I know that one of our horses (an arabian, incidentally) requires more sedative than our other (larger) horses. After finding this out the hard way, his dose has been slightly increased.