'Activity' is not equal to 'sport.' As I said, they all burn calories (at diff rates based on intensity), but sports activities are intense enough that risk injuries and you need to train to perform well.
This made me lol so hard I fell out of my chair at work. If all it takes to be a sport is injury risk, then disc golf qualifies, along with bowling, golf, ping pong, darts, and pool (ok, those last 2 are a stretch). Seriously, you must be heading out to the course throwing everything 100 feet if you think injury is not a real possibility in disc golf. Even with proper form, you're putting a ton of strain on your larger muscle groups as you rotate cleanly through the shot and maintain a stable base with your lead leg. I can use golf as a parallel here, but rotator cuff injuries in golf are super common, so are knee problems and hip problems. These same things come into play with proper rotation in disc golf.The only thing that makes you more likely to blow out your knee in say football vs disc golf is that you have people consciously trying to knock you down while you play.
On the training side of things, hell yeah you need to train to perform well in disc golf. Top level players aren't carrying a 12 pack on their shoulders and playing 18 holes with one beat up Valkyrie that they throw 100 feet. These guys (and women too) are bombing drives, carrying 30+ discs, hiking on relatively difficult terrain and doing it all while using a large percentage of their muscle groups to power the disc. Let's compare this to a line-man in football who wears a hefty amount of pads roughly equivalent to the weight of the equipment a DGer is carrying, uses mostly lower body strength for short bursts and does not have to hike anywhere and also gets to take a break on turnovers. I'll be honest with you, if I wasn't built like a twig, I'd probably be opting for the short bursts of physical activity vs. a long sustained energy output required to play a DG tournament. I am not built like a linebacker, so I play disc golf. The training to be able to perform at a top level for many holes during the course of the day is high. Sure, I could not train and go duff around throwing 100 footers like you, but I want to perform well, so I throw in the practice field a ton, I condition my body, I get mentally prepared.
Your argument is just poor in general. Pretty sure an activity is elevated to sport status when you have to practice daily, get physically fit, build muscle, work on balance, and sharpen your mental game to even have a chance to hang. This is what separates a sport (like DG) from a game (like playing catch with your friends)