I believe that children should be spanked because if you let them get away with a lot of stuff they will be labeled as a menace to society. They will more than likely turn on you also. But I do agree that some parents go too far as to spanking children like using brooms, extension cords, etc.
The Torah/ Tanach/ Old Testament Bible states in Proverbs 13:24 that He who spares his rod hates his son: but he who loves is son chastises him betimes.
My interpretation of this precept is if you discipline your child/children when they are young, he/she/they will grow to not only have that level of fear of their parents as all children should, but will also have respect for their parents as well as other adults and self control in the face of temptation.
I know from experience as a child, as well as a parent of 7 children, that a spanking every now and again may be warranted for some behaviors, when modern forms of punishment are unsuccessful.
The behavior of young adults is always on a decline. I won't make the broad assumption that a lack of physical punishment is to blame for all the 20-somethings that act like children but I will say that children need structure.
Yes, the best way to give a child structure is through a consistent and loving family however, some actions will only truly be understood when you spank them. I would say spanking can be an effective tool until your child reaches a certain maturity level and that could be anywhere from 3-10.
Spanking is useful when a child will not understand not to do something if you simply explain it to them. If you live near a creek and your child is constantly playing near the water, regardless of what safety nets or warnings you provide, then a spanking would work appropriately. If the child associates physical punishment (that is rarely used and thus significantly more effective) with the creek then they are much less likely to go there.
Obviously beating your children is never appropriate but history shows us that smacking your kids ass will not result in them being violent or aggressive. Kids today are allowed to get away with too much. Obviously we want them to be free to grow and be creative, enjoy a nurturing environment, etc. but if they don't have structure and discipline then they will simply behave when you're around, not because it is the right thing to do.
A parent should be allowed to chose the way they discipline their child. If they want to spank them, then so be it. Nobody should have a say in it unless they are seriously harming the child. Many people spank their kids. I have no problem with it unless it is excessive.
Parents should never use spanking as an option to discipline children. Spanking is violence, and teaches children violence. If a parent can't take time to talk to a child, and patiently explain something, then the parent is not "raising" a child; a parent is simply enforcing his or her will by corporal punishment. Very bad idea.
Spanking children can often be a gateway to abusive types of discipline and even just spanking itself can seriously harm a child if done wrong and many times, parents will simply spank while angry and possibly cause damage to their child. It shouldn't even be an option because it is far too easy to "go too far", and there are many other options out there for discipline that don't involve striking a child.