Sarah Kuttner, a 37-year-old author, kick-started the latest debate with a Facebook post that took aim at inner-city bark-wetters.
“Mothers who hold their kids up against trees to pee in the middle of a neighbourhood full of cafés and, by extension, toilets: no!”
Like-minded non-parents wasted no time in venting spleen at “shameless mothers” and their “brats” in an avalanche of comments that at times bordered on the hateful.
Psychologists worry that parent-bashing has become almost a national sport in Germany. Keyboard warriors revel in mocking parents for giving their kids apparently pretentious names, like Karl-Emil or Iphigenie, while books on anti-authoritarian and over-protective parents fly off the shelves.
A Berlin café owner who erected a concrete bollard to keep out strollers in the gentrified Prenzlauer Berg district was greeted with praise: “Finally,” said one online fan, capturing the mood among sippers who like their coffee with a dash of silence.
Andreas Engel, a psychologist who specializes in parenting, likened the criticisms levelled by non-parents to football fans shouting tactical advice at their television sets.
“Everybody, absolutely everybody, has an opinion on child-rearing,” he told the DPA news agency.
But parents and non-parents have grown further and further apart in recent years, he added, a development he attributed to Germans having smaller families, women waiting longer to have children, and the growing number of couples who decide not to have kids at all.
“This of course results in a loss of knowledge about what it's like to live with children, and of the ability to empathize,” said Engel.
“Anyone who has lived with children knows that you can throw the notions you once had about child-rearing in the dustbin.”
Part of his job now involves helping parents deal with unsolicited advice from outsiders, he said.
Official statistics confirm Germany's changing family structures. The average age for first-time mothers in Germany is currently 29.5 — four years later than in the early 1980s, and seven years later that the average at the time in the former East Germany.
Also, a fifth of German women aged 40-44 do not have any children.
But are parents also to blame for a hardening of attitudes? Anja Maier, a journalist and author, has followed closely the growing domestic culture clash. A couple of years ago she wrote a book bemoaning the “macchiato parents” taking over Germany's inner cities.
And while she finds the spiteful tone in the current debate shocking, she does still think parents need to get a grip.
“Every family these days is a little debate group,” said Maier. “Does everything really need to be debated? Does it all need to take place in public?”
And don't get her started on children in fancy restaurants: not a huge fan.
She also reckons modern parents are chronically dissatisfied.
“Parents are always moaning,” Maier said, despite Germany becoming increasing child-friendly.
“There are a hundred times more playgrounds than when I was growing up, there are children's museums, parent-children cafés, more and more play streets, and adventure forests.”
Yet still parents get upset if their kiddy-winks aren't welcome in a café, said the former MTV presenter.
“There's no keeping them happy.”
Her strident opinions have seen Maier take heavy abuse in the pee-on-a-tree debate.
But at least she has Moritz Freiherr Knigge on her side: Germany's go-to arbiter of etiquette advice views children peeing in public as an impertinence.