The owner of an espresso bar on the NSW south coast, who chalked a controversial message about Australia Day on a window blackboard has been inundated with death threats since a photo of the sign went viral.

The owner of Mister Jones in Bermagui said his business has been targeted by vandals and his voicemail flooded with threats after a local man photographed the sign "Yes, we're open on national dickhead day" – a reference to them being open for business on Australia Day, January 26 - and uploaded it to Facebook on Monday.

The photo was then shared on the Meanwhile in Australia Facebook page and as of Thursday morning, had been shared more than 3500 times and liked more than 7000 times.

The sign had only been on display for around 15 minutes and was placed there "on a whim", Matt - whose surname Fairfax Media has chosen not to publish - explained in a lengthy Facebook post on Wednesday.

He said the response had been "disproportionate", with vandals having even drilled the door locks out and glued the windows shut to attempt to prevent him from opening on January 26.

"Over the last days, messages have been cascading through my email account, containing unprintable abuse and describing group plans for physical attacks," he said.

"My voicemail account has mercifully reached capacity and I've long stopped listening to the graphic and explicit death threats. These messages have been much more chilling than the thousands posted online."

Matt said the deluge of vitriol has "far surpassed" any meaning that could be reasonably inferred from his "simple chalked jibe".

"The provocative blackboard seems innocuous now, entirely disproportionate to the scale of the hatred. Indeed, taken on face value, the blackboard was possibly the most Australian thing that one could write about 'Australia Day', in a country that claims to be proud of its 'larrikin' irreverence and self-effacing humour.

"Over the past days, my espresso bar has been used as proxy for Indigenous Australians, Islam, refugees, homosexuality, class, Asia, immigration and much more.

"The bloodthirsty outrage, white anxiety and bitter intolerance was not a necessary response to the blackboard. For two days the blackboard has simply been a convenient repository."

Rob Grimstone of Bermagui took the original photo of the sign because he "was disgusted in it as an Australian".

"It's just not right," he said.

Mr Grimstone said he had also received a call saying radio presenter Ray Hadley mentioned the incident.

"I never expected it to go as far as it has, but I'm glad it's gone viral," he said.

But all of the publicity may have actually worked in Mister Jones' favour.

Matt said while many of the online comments online "gloated" over the "inevitable" loss of business and the "demise" of the espresso bar - which he runs as a side project in his art studio - he actually recorded his biggest Australia Day crowd on record.

"Many people travelled from as far as Batemans Bay in the north and Merimbula in the south to drink a coffee and have a laugh. Among these supporters, we were particularly happy to welcome esteemed members from some strong, local, and largely marginalised communities," he wrote.

"Arguably, [my blackboard] offended those who experienced a moment of self-recognition. As these individuals continue to overreact, the sign only becomes truer.

"The shoe clearly fit, and they wore it."

With the Bega District News