What a silly set of arguments. Exercise is literally empty time for you with no other benefit? Lets put aside the fact that you receive endorphin from almost any exercise you do. You can't go to the beach, rock climb, play with your kids/dog, etc.? No, must be productive all the time. Even if that was the case, it's quality adjusted lifespan that counts for most people.

You may break your wrist sure. In the same way that you may get wrist injury from typing too much. Exercise will reduce the likelihood of other injury.