The argument that FAs need to pass a physical test seems to be the flip side of the "We're here primarily for your safety" argument. Being disgruntled doesn't interfere in your ability to open an emergency exit. Methinks that if there truly was a problem with the aging FA population not being able to perform their safety duties, the FAA would have already mandated regular fitness tests and/or mandatory retirement ages. You know, like they do for pilots.