Podcaster and cool guy George Hrab had a great take on the “you have too much time on your hands” comment.
The negative way to approach it is to respond with “So what have YOU accomplished lately?” But it’s better to go at it with the attitude of “Hey, I’m creating something. I’m building, making, composing, practicing something which gives me joy and occasionally even gives other people joy as well.”
Let’s assume that somebody made a scale model of the Sistine Chapel out of toothpicks. “Wow, this guy sure has a lot of time on his hands” implies that the time building the model was wasted. But who are we to say that somebody else’s artistic work is useless or valueless? It may not be art to us. But to somebody, at the very least, the artist himself, it’s a reflection of their passion. I think that having a passion like that and then acting upon that passion to create something has intrinsic value.