First of all, the steps the women were sitting on were not legal and have subsequently been removed because they were encroaching on a public beach. At the very least, the villa owners should have known this.
I wonder how difficult it would have been to have erected a low fence on the legal edge of the property, a gate to the beach, and a sign saying NO ENTRY in the required languages? It might have been enough to put off the "hordes of Chinese (?) tourists" that this man complained about previously from trespassing on his property.
A small private villa estate on Railay Beach in Krabi has such a fence and it stops undesirables from wandering around the property. At least it did last time I stayed there.
Finally, what happened with the road-rage incident Mr. Fehr was previously involved in? Or the dodgy elephant sanctuary where most of the "rescued animals" had been bought in?