Spare the rod and spoil the child. Your thoughts?

There are numerous studies that indicate the negative impact of using corporal punishment to discipline children, ranging from an increase in future violent behaviour, to intimacy issues in romantic relationships. I know I'll probably get a lot of backlash for this, since caning and physical violence is still such an accepted practice in Singapore, but I've never been able to understand why this is okay. We can't hit other adults - that would put us in jail. Why on earth do we think it's acceptable to hit children?