There is research done, by Christians and nonChristians, that goes both ways regarding spanking.
There is no research that has shown that spanking leads to aggressive behavior, or violence, or low self-esteem. There are studies that show that abuse can lead to those things, though. I know people who were not spanked who have much lower self-esteem than I do, and I received beatings.
I think that if we all do the best we can as parents, and try to keep the best interest of the child foremost in our minds, it won't matter what discipline techniques we employ. Our kids will know how much we love them, and they'll know we cared enough to teach them right from wrong, whichever methods we used to get there.
People rise to the standard expected of them. GC