This little stunt has generated 13 pages of commentary. If the moose rider was after 15 minutes of social media fame (infamy?), he got it.
I see evidence of yahoo behaviour all the time in areas where I hunt. The perpetrators are usually urbanites, not the kids of locals who live out here. They know better. ATV's and 4x4 pick ups roaring through fish bearing streams to create a mud bog (the better to get stuck in before asking a local for help getting unstuck), unattended fires during a fire closure season, litter of al kinds (to include beer cans and bottles which cannot be taken home for disposal), etc., etc.
Ask a Conservation Officer what he thinks about coming up on a moose in a power boat and then riding it. I believe the penalty for such an act would be pretty severe and make the guilty party look pretty stupid in the eyes of the law.
I live on a lake and it's not unusual to see moose or bears swimming across the lake. It has never occurred to me to harass them in any way as I realize they could be escaping predators and/or stupid people.
It matters not what cruelty or stupidity people have been guilty of in the past. We exterminated the buffalo, killed off the passenger pigeons, endorsed #### fighting and dog fighting for sport along with a host of other behaviours now regarded as barbaric. The best hunters I've known have had a profound respect for the game they hunt, often turning down shots, not willing to kill something just because they can.