Martial Arts originated in a different time and in societies which had different customs and rules than ours. Yes, there is discipline involved - but - it is not an excuse to "check" the rules of our society at the dojong door. Although I know Master Preira and his wife - they are very fine people - I am also a parent who would be outraged if my child were struck by an adult, especially by an instructor in a non class situation in reaction to a personal insult. No matter how it happened, a Master needs to take such a charge seriously - s/he owes that to the parents in whose care s/he have entrusted their children - and who are paying for that care.
If the parents were overly aggressive in their approach, it's on them - but - if it had been my kid, that might have been my reaction also.
As aside, although I do not mean to say this is necessarily the case with the Preiras, I have seen repeatedly where Masters somehow begin to believe that they are masters of far more than than martial arts. When this happens they can lose their persective and not be able to view a real world situation the way parents -(or police!) - may view it.
I truly admire a dedicated martial artist but cannot condone the way many of these schools create a world within a world - a cult-like atmosphere if you will - where you must accept unacceptable behavior because it is the "Martial Arts" way and the master says so. Masters and instructors must take GREAT care not to let all those "Yes, sir" Thank you sir", Master, etc. go to their heads. These are expressions handed down from societies with great value placed on such expressions of respect. We modern Martial Arts students honor those who passed their knowledge down to us by continuing to using them. We use them, however, to convey to the Masters and Instructors that we respect their greater knowledge of Martial Arts, but their use should never be construed to mean that we accord them greater wisdom than us - or the law of the land - in any area outside Martial Arts unless they have proved it to us otherwise in separate circumstance.