DY, actually I read the introduction and the main premise of the book is training children into good behaviour instead of letting them reach naughty behaviour. The example I read was explaining how to teach a very young child (an infant) not to touch something by placing the object near them and then telling them ‘no’ very firmly when they try to reach out for it. After a few tries they understand and no longer touch. Nowhere did I read of wholesale beatings into submission so any parent who seems to think that’s the case has clearly misread. Although I do think that perhaps they should have made the book a little clearer.
If you check his family background, you will see that they are religious Christians, and therefore they use this strict approach in conjunction with their own moral teachings. Unfortunately most non-Jews are not religious and would therefore not have the same judgement behind using stricter punishments. This is how you end up with parents hurting their children as a result of reading a parenting book.