The most common advice is to avoid above the shoulders; the kidney area; and places where you can easily feel bones under the skin such as the spine, sides of the hips, shins, etc. I guess that reaction may have been caused by the pictures of whipping your back near your kidneys (which are located just under your ribs if I remember my anatomy correctly), which risks damage so is obviously not in the interests of the bdsm community! I would be interested to know why the pubes area is particularly unsafe, as there are no internal organs there and the front of the pelvic bone is quite well protected - unless the objection was that "wrapping" could easily occur and risk damage against the sides of the pelvic bone.
VV