A few thoughts beyond the many comments which with I mostly agree (agent bad day, horrible WX, pax responsible for WX hotels and should know that):
1. Delta is one of the only programs, to my knowledge, that has specific language in its T&Cs that basically say "we don't allow Mileage Runs":
Originally Posted by Delta "Mileage Credit Rules & Conditions
On connecting flights that require a change of plane and flight number, mileage credited will be calculated based upon the distance from origin to destination for each segment of the trip. However, use of connecting itineraries in lieu of nonstop and/or direct flights for the accumulation of additional mileage is not permitted. Delta reserves the right to limit mileage credit for an itinerary to the number of connecting flights actually traveled or the maximum number of segments shown in Delta's published schedule for a connection between any two cities, whichever is less.
http://www.delta.com/skymiles/about_...ules/index.jsp
Thus pushing too hard for getting full credit may backfire. Getting nasty about it certainly will.
2. Most airline employees don't really know much nor care much about the details and benefits of their employer's frequent flyer program. You need to put the "you can buy a ticket anywhere in the world for under $1000" comment into that context. Like the general public, the typical employee thinks that the sole reason for saving up miles is for a "free ticket." Yes, even the employees whose jobs include processing upgrade lists and doing priority boarding still probably think of that as the only real reason for getting "miles". So those who have to fly a whole lot for work/personal reasons and primarily (or even exclusively) value the elite status benefits and don't give a hoot about RDMs are totally alien to their thinking.
3. It's the holiday season, it's a horrible weather event across the country, the economy blows, everybody is on edge. However bad the agent's comment was (and we still don't know the entire long story), maybe you should just let it go, forgive, and reduce your angst level by so doing.