I've always done this every day & haven't stopped since being diabetic. I actually thought it would be a good thing in terms of repeated injection sites.
Smug health care professionals; pretense, pomposity and presumptuousness; people who have a disregard for other people's health and safety; being "fenced-in"; arbitrary authority; nonsensical rules; political correctness; stupidity that masquerades as profundity.
The "warning" for diabetics might very well be based on what another poster has said, that sometimes we lose sensitivity on our skin and therefore wouldn't know if we are bruising ourselves by brushing too hard. Currently, my main concern are my feet, and I do a form of dry brushing on them a few times a week by using a pumice stone. For the rest of me, i sometimes use a natural fiber clothe, and so far no problems.
I would imagine that we are more prone to flaky, dry skin than others, so getting rid of this mess is a good idea, unless parts of our bodies/skin are numb and have loss sensitivity to touch.