I was raised and very quickly did I learn from right and wrong.. And it wasn't because I was told to sit in a corner for 30 minutes with out talking... Its because I quickly learned that if I did something I knew i wasn't supposed to do I would be disciplined, and that is associated with pain. I never broke a law growing up, never smoked, never stole, never drank underage.
Is there a line, yes there is. There is such thing as child abuse, but it is not the same as disciplining your child by spanking them for doing wrong. Child abuse is much deeper than a spanking.
When I bring a child into the world, I intend on raising it just as I was, and it won't be child abuse.