We have had this discussion on ScubaBoard many, many times. The English language has had many different uses for the word "sport" over the centuries. Read the magazine Sports Afield, and you will learn that shooting ducks is a sport. Gambling is often referred to as a sport--betting on horse races used to be called "the sport of kings."Scuba is never a competition and is therefore never a sport. It’s a hobby. Like hiking for example.
What all those past threads have boiled down to is matching each poster's personal definition of "sport" to diving. Each opinion is therefore correct.