I was spanked and smacked as a kid and then sometime in the 80's the line got blurred between discipline and child abuse, and then it suddenly became criminal. My mom went through a phase where she claimed she didn't remember ever hitting us as kids, and over the years I've had to remind her of a few episodes. That said, I see kids now and how they behave in restaurants or shops, and know without a doubt had I behaved that way as a child I would have gotten a wicked spanking. It seems now even though there is a difference between hitting a kid and physically restraining a kid, there will always be someone that views any physical intervention as abusive - and it can prevent the parent from doing what may be needed.
i remember some bullshit therapists/advocates years ago constantly saying that instead of using the term "spanking" it needed to be called "hitting" because that's what it was. so ridiculous. an open hand to the ass is far different than a closed fist to anywhere else on the body. on the rare occasion we spank our kids' hands when called for and have no qualms about it.