An interesting essay, but I believe shaving is common enough these days that no doctor would think twice when seeing it.

Minor abuse is lawful in every country, if consented to. If it would not be, you could not engage in sports like ice hockey, football, wrestling, or boxing, neither submit to surgery. This also applies to such things as spanking when the spankee is a consenting adult. Remember that a normal BDSM relationship inflicts less damage than many ice hockey games - how many has to stop their sex games because of numerous concusions, the cause Eric Lindros had to stop playing ice hockey.

The main reason the legal authorities does not view spanking as minor abuse or something you could consent to is prejudices. It would be good to get rid of such prejudices, even if it would mean the BDSM play would lose that edge that it is somewhat "forbidden".