Sort:  

I might disagree with this. It's mental gymnastics and stamina and training is definitely involved.

That is like saying you need mental stamina to play a video game for hours, it is basically the same thing. Not a sport. Ice Hockey is a sport, even Golf I can give the nod to. Chess is a board game not a sport.

Pssst... I'm telling you a secret: "you need mental stamina to play a video game for hours", it's called eSport. ;)

This is what it takes to make it a sport: https://en.wikipedia.org/wiki/Chess_boxing