I'm so confused about #2. How is shaving his body hair more like ear piercings (which often leave a permanent scar even if/when the piercing closes) than a hair cut? Unless, of course, LW still believes #1, that shaving permanently changes the color and texture of body hair.

It's possible to give yourself a pretty bad cut with a modern safety razor (I have a little scar on my foot from dropping my razor just wrong) but the solution to that isn't telling LW's son he's not allowed to shave - it sounds like he'll sneak and do it anyway - but to say, "I only want you using a razor with supervision" like any other potentially dangerous tools young(ish) kids learn to use, like steak knives or whatever.