Im really not trying to be rude when I say this...but...Rearing that frequently is a training problem. There is something going on that has more to do with a horse that just likes to rear. Just my opinion.
I don't see the benefit of a punishment over a training correction nor see the benefit of smacking a horse around the head. I don't know how many horses you've smacked in the ears with a crop, etc but perhaps you were lucky to not have had consequences.
I have seen and had to correct a lot of horses with head shy issues and they all stemmed from a previous owner thinking that was a proper way to discipline.
Again, can't see the video so I can't really see why the horse seems to be rearing, but hoping a continuously rearing horse won't go over or that flicking it ears will correct the issue is how a rider will end up seriously hurt.