When did it become okay to ask a woman if her breasts were real?

Especially in a grocery store when she has a two year old sitting in the cart, wedding ring on her hand and is talking to a friend about her mother's recent surgery.  Is it an accepted intro for conversation now?  I missed that memo.  Didn't help that the guy made a squeezing motion with his hands towards my chest, as if to ask permission to feel for himself.  The mommy in me wanted to smack his hand and say, "No!  Shame on you!", but I opted for the look of disgust, met by his clueless "WhatdidIdo?" expression as he walked away.   And why is it assumed that everyone with ample bosom is falsely enhanced?  I'm not the first woman on earth to be naturally buxom.  Or am I?