Yes, big difference between spanking and beating. But spanking is definitely effective, as is evidenced by the many thousands of years of success in behavioral corrections when done properly.
Sadly, some have been successful in pushing the "intellectualizing" of child raising, which sounds great, seems enlightened, and IGNORES a very poignant reality about humans. We learn everything, and operate very little on instinct. I believe many in the more intellectual vein have forgotten that intellectualizing can only happen after one has developed their intellect. Children do not fall into that realm, do they?
Every child born into this world is born ignorant, and selfish. Selfishness is actually one of the few instincts we have, and when allowed to be embraced by the child, bad things result. Lack of respect, lack of discipline, lack of work ethic, lack of responsiobility. THese elements are what need to be taught, and reinforced for the child's best chance at a good future.
When a child is young, say from age 2 to age 9 or 10, reasoning will not work. Certainly, the older a child gets it is not without reason to believe that their own sense of reasoning and right and wrong will form. But if left without guidance and governance from the parents, this will not form properly. Remember, when we are born, we do not have a concept of limits, what is acceptable, what must be done. When one has no understanding of this, a parent has two choices. Either attempt to reason (which, with a lack of reasoning development, is as effective as pushing water uphill with a slotted spoon), or use the basic element every creature understands - fear.
For if one fears the consequences of electing to engage in bad behavior, that healthy fear of the consequences, once known, acts as a deterrent, or at least causes pause for thought before the act is done, or decided against.
I agree that spankings should not be done out of anger, although that is easier said than done. When it comes to children and dealing with discipline issues, it is best to remove all emotion from the equation, including anger and disappointment. This sounds like an easier said than done thing, but, when logic is applied, and the efforts of parenting are to raise your child be have the best chance of success when they grow to be adults, it becomes what is best for the child, regardless of how you feel about it, or how their actions made you feel. Feelings have nothing to do with it, beyond the love and caring to see the child through to successful adulthood, and that takes many years, commitment and consistency so that rules today are constant with same rules for tomorrow (in terms of right and wrong).
But a physical response which leaves a bit of pain and lots of lasting awareness is oftentimes the only effective means of getting the point across. Just like touching a hot stove drives home the fact that very hot can hurt you, so stay away from very hot, so too does spanking drive home the consequence for disobedience and destructive behavior.
We have not changed as a species, folks. We have advanced our technological know how, but in terms of the basics of human nature, it hasn't changed one iota.