this is an issue like religion and politics that people are endoctrinated to believe one way or another. Most people can't see any middle ground.
I personally believe it depends on the child and the most effective way to discipline them. I am purposely not divulging whether or not I believe in it because of my professional responsibilities. I know plenty of families that have kids that have been spanked many times and are still brats and just as many who've never spanked, and their kids are just as awful.
I think we all do our best, and some people are so afraid to be parents that they seek affirmation from complete strangers instead of stepping up to the plate and being a parent. Walking out of a store is a great example of being a good parent. Having young children who don't get what they want (snack, tv show, etc) without saying "please" and "Thank you" is another example.
Most of our friends either don't care what other people think of their bratty kids or are so oblivious that they've created monsters that are hard to be around. There are a handful of kids that are a pure delight, and we take every chance possible to let the parents know how obvious it is that they've put the time into being a parent.
I will say this much - beating and spanking are different. Yelling at a child can be just as damaging, calling them names, berating and belittling them can have deep psychologic scars that are just as hard to heal.