Those who live in glass houses have been well warned.
As have those who are without sin.
Truth is, I'm unsure why we're cautioning only these demographics. Because bar the homely Kiwi habit of skimming pebbles across rivers, I struggle to think of a good reason for throwing stones.
More to the point, the wanton and continued terrorising of an elderly woman in Havelock North by a persistent unhinged rock throwing assailant is simply unfathomable.
Some idiot, or a thicket of idiots, has been hurling sizeable rocks at Violet Wheeler's home for the past seven weeks. The besieged pensioner now has a veritable geological collection on her dining room table.
The 75-year old has endured seven weeks of not knowing who, why or when. It has her stumped. "I've never had an enemy in my life", she said after the most recent aerial volley on Sunday.
While it's not the most aggravated of crimes, it's a contender for the most heartless.
Not only is the culprit targeting an elderly woman living alone, it's been done at a safe distance, anonymously and under the cloak of darkness. You'd be pushed to come up with anything more spineless; faceless bullying which ostensibly scratches some disturbing itch.
Flaxmere's Henare O'Keefe, who lights up any room, will be lighting up his famous tunutunu barbecue to rally support for Ms Wheeler this weekend.
Here's hoping the imparting of his sense of community will either curb the behaviour, or convince the perpetrators to crawl out from whatever rock they're hiding under.