Personally, I think it's a cool photo, whether it be intentional or not. And for everyone saying you shouldn't pull on a rearing horse's mouth- I think it's a pretty safe assumption to say any rider has made mistakes, yourself included. I know I've certainly had PLENTY of bad moments. That doesn't make me a bad horse person, I just try to learn from them.
Anyway, I don't think a photo like that encourages any negative behavior. If people chose to try to get their horses to rear, it's their business. And the people who want a rearing horse will do so regardless of a picture posted online. Just my two cents.
Worth The Wait <3