Before uttering another word, I'd like to acknowledge that this is indeed both a sensitive and emotive subject and I am in no way passing judgement on anyone else by expressing my own views.I also received plenty of physical discipline at early ages, including hands caned witn a ruler from 5 years old and the cane from about 8 years old, so I appreciate what's behind the logic you express, even though it has no factual basis.
But I believe your concluding sentence is completely wrong, physical discipline is all the more important for minors. The psychology is well understood, the younger we are the more important our sense of self over others. Indeed up to three years old, there is no sense of "other", so appeals on behalf of others interests can have no effect.
That's why all higher order animals physically discipline their young at their very young ages, simply because they don't have the "other" learning capacity they gain later.
As much as we resent the physical discipline when very young, it does work as the crime and prison statistics of half a century ago and now show only too clearly.
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Ignoring morality for a moment... Flecc, did you ever receive physical discipline for the same behaviour twice? If so, is it not arguable that it was ineffective as a means of teaching a 'lesson'?
There have been many hundreds, thousands, (millions even) of social changes over the last half-century. Why link the increasing prison population to changes in attitude to hitting children?