Sanity is Optional
Look, I love the marching band. They're awesome, but they're NOT a sport. It's just them putting on a musical performance in a certain way. It is, by no means, an actual sport.
You obviously have no personal experience performing in a marching band, then. Yes, it is a musical performance; but much more goes into it than just that. Strength training, endurance, focus, and countless hours of practice go into "putting on a musical performance in a certain way". My high school, and countless others, have a pay to participate policy for SPORTS programs... guess what I had to pay to do? That's right, marching band. There is no such fee for choir or symphonic band. That performance out on the field is more than just musical, it's a very physical ordeal. If something as asinine as Frisbee Golf can be considered a sport, then surely something much more challenging and demanding such as marching band is an even better qualifier. How about YOU go practice 5 days a week for 2 months in the blistering summer heat to put on a 'musical performance', continue practicing 3-4 days a week for weekend contests where you COMPETE against other bands, and THEN tell me if it should be a sport or not.