Discipline is necessary. Verbal discipline is not always adequate.
I don't care what the hippies say - I want my child to stay in line when out in society, not being in jail when they are 18, thanks.
If you take behaviourist theory, you will see that physical discipline is a punisher, rather than negative reeinforcement. There are certainly better ways to "correct" child behaviour (Negative reinforcement), but neither behaviourism or I think that punishers should never be used. Sometimes you need to use a punisher.
Should you smack someone elses kids? Nope!
So what you're saying is if I don't hit my children they will end up in prison? I would be far worried about it working out the opposite way around, if you want to talk about extremes of a situation.
I can see, your point, but I still disagree, there is enough alternatives for it to be avoided, completely. I guess it's just a matter of opinion.
Generally I'm against it, but there's no single approach that works for every kid.
Some parents tend to forget the whole point and beat their kids as a form of retribution rather than corrective measure. In my ideal world, i think physical punishment should only be used in case the kid does something intentionally and contrary to your warnings (eg, not break a vase by accident). Maybe even use 3 strikes system.
PS:
If your child goes out into the real world assuming that time-outs are the most severe punishments are "timeouts", he's in for a rude awakening when a bunch of skinheads beat him to a pulp.