to have those people get life-threatening health conditions during routine workouts
I think the 'routine' bit is the important thing. A marathon is not a routine activity done day in day out (unless your undertaking some sort of extreme challenge), it's test, and a demanding one. The idea that everytime you step in a gym you must be engaged in some sort of gruelling, do or die struggle is just daft.
There was a video of Greg Amundson on CF.com a bit ago, and IIRC he said something along the lines of "these workouts are designed to humble the worlds greatest athletes", and I thought, what, are they not designed to just make people fitter? Is that not what you look for in a fitness program?
(The idea that the 'World's Greatest Athlete's' are actually doing crossfit is another one that might prove slightly contentious as well....)