Yes, Larry's reply confirmed what was said in the Desert Sun article, that rappelling off of old nylon slings is a common practice, though one that should be combined with some judgement. In another communication, Larry used the term 'life-saving paranoia'. I like that term.
We used to make our slings in a few minutes over the kitchen table. Cut the webbing, tie it into loops, seal the ends with a match. It was standard to carry seven: four singles, two doubles, and one triple. After a year or two of heavy use you threw them in a trash can and made another set. Today people buy slings factory-sewn into loops. Said to be safer than a knotted sling. I checked my knots before a climbing day, and never worried about them during a climb.
I hope this does not deter people from rock climbing. I view driving on the Santa Ana freeway at night in a rain storm as dangerous, stressful, and an activity to be avoided if at all possible. A weekend of rock climbing at Joshua Tree should be challenging, if you want to make it challenging, but fun and relatively safe. Hiking Skyline has a wider ranger of hazards not subject to your control.