The thing is though that I absolutely do use my size and strength advantage against DD1 if she is very naughty, e.g. to remove her from a situation where she has hit, or us about to hit, another child.
I will pick her up and move her to another room totally against her will. And I'll be cross when I do it.
When she has tantrums I just sit down next to her and look bored and ask her periodically if she's finished. Then when she's done we have a cuddle. But if she hurts other children I will remove her, and that seems as much a kind of violence as a light smack on the bum. But I would never do the latter.
And yet I do the latter sometimes when I play her like an orchestra (bottom = bass drum, fingers = bells etc.). So it's not the physical act of smacking that feels wrong. In play I tap her bottom just as hard as I imagine someone who uses smacking would. It doesn't hurt her, she thinks it's hilarious.
But if I did it to chastise her then it would be physical touch to punish, and that feels like it would humiliate her.
The relationship you have with your children is very physically intimate - you cuddle them, you change their nappy, you put cream on their rashes, you tickle them -a parent's touch should always be kind I think.
Their little bodies that I made inside mine and nourish/ed with my milk - the thought of physically hurting them is viscerally wrong.
I know I'm far from alone in feeling that physical pain if they hurt themselves, particularly if it was through my fault. I will never forget the how I felt the day DD1 rolled off the bed