Wrong according to who? A child cannot always be reasoned with, because their brain is not completely developed to have full logic capability. In order to correct their behavior it is NECESSARY to do it if verbal correction fails.
Doing serious bodily harm to a child is necessary?
The problem is that the parent wasn't consistent in the child's formative years. "No" became "Yes, because I give up." Parents keep counting to 10 while their children misbehave at Wal-Mart and instead of getting to 10 and then taking the child home, they keep restarting their count with "Billy, are you listening? I'm counting to 10! One, two, three-- Billy, I'm counting to 10! One, two--".
Parents don't enforce consistent bed times and waking times. They don't control what their children eat. They don't make their children do even the most basic of chores, and when they do they put up with their kids' incessant whining about how it's not fair that they have to roll the trash container out the the curb in the morning and then push it back to the side of the house when they get home from school.
And then these parents are surprised when at seven years old their kids have discovered (through logic) that there really aren't any consequences to their actions. At that time, the worst of parents result in beating their children. Not a spanking, not a single swat to the rear (and even that is wrong, as it only teaches children that might makes right, which again, would be a logical conclusion for them), but an all-out full-blown beating.
These children end up crippled (either physically, emotionally, or both) or they end up dead.
Children learn what they are taught. If you want to teach them German when they are young, speak German to them while they are young. If you want to teach them that discipline and chores are necessary, give them discipline and chores. If you want to teach them that it's OK to bully people, to hurt those weaker than themselves, and that one must obey without question those who are stronger than themselves, by all means beat your children.