No, it shouldn't be acceptable or ethical. Parents who need to beat their kid to get their point across seem to lack parenting skills. There are many ways you can punish your kids without inflicting physical pain.
What disciplinary action should be used in the worst case scenario?
Depending on age there are many things you can do to teach your child a lesson, in teen years it's all about image, so embarrassing your child is a lot worse to them then actual beatings.
My parents used corporal punishment, and never beat us.
Um what? Your parents punished physically but never beat you? That's a confusing statement.
Most people realize there is a difference between a spanking and a beating.
And yes, sometimes a spanking IS necessary.
Unless you advocate parents being able to turn their "too stubborn" child over to the state.
Corporals must be punished.