Have you never seen that tribe that push their penii inside out into their bodies?
Oh of course. There are some wild tribal bod mods, lip plates, skin beading, neck stretching, tooth sharpening, nearly all of which in the US would be considered child abuse if done to an infant here. Globally we're all over the place as a species considering what is culturally appropriate to do with your/your child's bodies. I've worked in both the piercing and S/M cultures, humans do some whack stuff to their junk; even in the US. As far as what cultures other than mine do, no judgement. Not something I'll be doing any time soon, if they want to tie their manhood inside out, that's groovie and one hell of a party trick. I gotta ask is it worth it?
As to circumcision, yeah, it's pretty much standard in the U.S., the CDC, Mayo Clinic and a whole slew of research agencies have a ton of data about STD transmission and later life medical problems that circumcision in infancy helps prevent to a degree, as my dad found out. Most U.S. pediatricians will recommend it.
I remember in college some kid-activist came up to me telling me how angry I should be about being "mutilated as a baby." I replied with, "Uh, what?"
We've got activists for and against everything here.