"Shame on you." Parents receive an anonymous note judging their living conditions.

Kelly and Mike Bruning have learned the hard way that once you have children, you become prime targets for unsolicited judgement from strangers.

The US couple recently received an anonymous letter, addressed simply to ‘Parent,’ accusing them of being “about the most selfish parents around.”

The reason for such a strongly-worded message? The fact they live in an apartment.

“Because you like the beach, your boys are trapped in a tiny, one bedroom upstairs apartment,” wrote the stranger.

"Kids need [a] yard to play in. A swing set, or trike to ride when they want to, not just when it's convenient to you."

The letter ended with the words "SHAME ON YOU."

Shocked by this uninvited criticism from an anonymous sender, the Brunings posted a photo of the letter to Facebook.

"Now… this place just got interesting," the couple wrote. "Sometimes harassment comes in simple forms."

The post garnered a strong response from the online community, with hundreds of people leaving comments in defense of the family.

"Yeah shame on you guys for taking your kids outside every day and letting them play on the beach, in the sand, the water and other activities..." wrote one Facebook user.

"Unbelievable that someone feels they have ANY right to judge you as parents," wrote another.

"Ridiculous!! It's not about the size of the house you grow up in, or the size of your backyard that defines a child … what kids remember is the time their parents spent with them, how safe and loved and supported they feel growing up, being taught about what's truly important and it has NOTHING to do with the size of their home!!"

Surprised by the overwhelming support they received from their post, the Brunings posted a thankful reply.

"Thank you all for your wonderful responses, thoughts, input and advice," they wrote. "Which turns out to be the ultimate 'Open Letter' to the ignorant coward who bothered to write and send this junk mail."

"See you all at the beach - the "infinite backyard"… (only after we unlock our boys from the hall closet which doubles as their bedroom and bathroom... I sleep on the kitchen counter)…"