I should point out that AMTRAK (a government company) has on the Northeast Corridor Trains a quiet car where loud conversations, cell phone use, and music are prohibited. I do not see many people challenging this rule and it does not seem that AMTRAK has removed this car from service.
Obviously a train and a plane are two different forms of transportation and arranging a quiet section on an airplane would be a little harder but I do not see why it could not be done. One of my biggest complaints with SONG is that I find it counter-productive for accomplishing paper work in-flight. Frankly, SONG is too much of an in-flight party for business people but, it is a great airline for those heading of to vacation.
Personally, I feel that DL should supplement its SONG flight with one of two mainline flights for those people who prefer a quieter ride and a place to finish work before hitting the ground. (I know a total pipe dream but, hey you never know!

)
Dan