Hitting kids is teaching them that hitting is OK.
I saw a woman beating the shit out of her 8 or 9 months old child this morning. Literally smacking it in the face, yelling at it to shut up, over and over. Since I have just taken my concealed carry carry class, I had just learned all the laws on using force in defense of others. I walked up and told her, calmly, that what she was doing could be deadly to the child and if did it again then I would have to defend the child. She yelled at me and I just stood there, waiting and looking at her. Eventually she walked off in a huff.
I hope she doesn't take out her poor parenting and life skills on her child.