Oh boy, are liberals now so stupid we have to explain this to them?
That said, back in the stone age 50's and 60's, when my mom and her friends were having kids, I don't remember people doing this. It seems to have come into vogue with New Age, Alan Alda, Dr. Phil era. Except for my wife, I would never rub a pregnant woman's belly without permission. But I can't see charging someone with a crime unless they are a stranger creeping out a lady.
The maternity clothes worn these days are also much different than what women wore just a generation ago, when it wasn’t really too classy to wear skin-tight knits that showed every skin cell on the baby belly.
I just don't understand this concept. I love to rub, and rub, and rub ANY and EVERY women's pregnant belly, murmuring something about 'tasty snack' and 'lots of protein' the entire time.