Delta is entitled to have whatever rules they set for their frequent flyer program, and if it were clear that Harrell deliberately flouted those rules in an attempt to cheat, it would be fair for the airline to take away all of the cello's miles and some portion of Harrell's FF miles, or even all of them, as a penalty.   It's also 'fair' for an airline to refuse to insure musical instruments against damage or theft when they are checked, refuse them as carry-ons even when they fit in the overhead compartments, and then allow their baggage handlers to throw them around recklessly.

Fair? Sure, I guess. But is it good business practice? Are stories like this or the "United Breaks Guitars" story good publicity or marketing for the airline?

Delta couldn't really know that Harrell had received their "warning" letter. (He may or may not have, given that his secretary handled his business correspondence.)

But to treat him like some common criminal, after he had paid for two tickets every time he flew with the cello, and add the overkill of barring him permanently from their FF program, that's gross overkill and horrible customer relations.

I hope someone does put together a clever song about this and put it on YouTube!