"When I watch musicians that I respect play, they can all play straight off sheet music. That is how it should be. Anything less damages our culture"

This presupposed that music in our culture was composed and entered into the tradition via a written down form.

Sheet music can only be a snapshot of how one person has documented another persons playing, and by taking this as definitive loses everything that makes it part of the culture. How can one tell what the person who made a song or tune intended from a third party documentation.

What sheet music cannot capture are the nuances that the musician/performer adds to the notes - subtle (or not so subtle)improvisations, variations, the warmth of the tone - things that a skilled musician can do which cannot be documented.

I think it was Leonard Berstein who said that it is easy to tell the difference between a person playing or a machine. The machine is note and meter perfect and totally lacking any aesthetic value, whereby a person's imperfection is what makes music pleasing.

In my opinion, the greatest musicians are those who have the ability to interpret music - if you listen to a recording of them playing, and you know their work, you can tell who it is in an instant.