hey, yea i rode a horse for awile that did that but she was 14 3 so it wasnt too much of a problem haha
first, as always rule out any physical problem that would make him resent bridling (get teeth checkd, check for sores, parts of the bridle that might poke him, etc)
if that all checks out, he could be associating hte bridle with hard work. try to have a day where all you do is bridle him, handwalk him around,then unbridle him an dturn him out or soemthing. after 15 minutes or so, bridle him again then unbridle so you start disconnecting the bridle with a negative idea with your horse. you could also have a couple days where you just hack around and have fun days.
when youre bridling in his stall (when you ahve a lot of time and patience), try to wait for him to put his head down. simply put hte bit in his mouth, and if he walks around, stay with him and dont give up. dont pet him or anything until he puts hs head down. even if it is just a inch, pet him a lot and say good boy. keep doing this until his head is low enough for ou to slip the rest of hte bridle on.
given this would kind of suck to do a lot, but its worth a shot
lol and also i would go with your idea of submitting to pressure on his poll, or giving him a sugar cube whenever he accepts the bridle (its horrible but im a full believer in bribery lol)
basically just try to make bridling a happy experience for him and try not to make anything uncomfortable for him if he is doing what you want