Statistics have to play some part in this. What percentage of all drivers (or of all drivers of cars over 5 years old, or of all drivers of cars over 10 years old, or whatever) are driving old Benz diesels? Now, eliminate those among that group that are avid enough DIYers that they don't turn to Car Talk for advice. I would guess that what's left if a relatively tiny pool of potential callers.

If you search the archives on their site, you will find a couple of entries regarding old Benz diesels. In one of them, they caution someone not to continue using ether as an aid to cold weather starting.

There are a number of other entries on their site concerning other diesels. Browse them if you wish to see if there is any consistent attitude regarding diesels.