One particularly vile post said: "Its not racist because blacks aren't humans."
The milk bar owner initially tried to explain the note by releasing CCTV footage of eight dark skinned youths in the store, some of who menaced him while their mates stole from the shelves. He told 7 News they always came into his shop and stole things which made him "very angry".
The note was an impulsive reaction to the incident with the eight youths, he said, but claimed there had been at least 20 other similar incidents in the past.
A common theme from many Australians on various forums was that it wasn't racism if Sudanese people had stolen from him.
Many people made direct links to Melbourne's youth gang crisis and spiralling crime rate. "The black c**** are on the news rioting and rampaging every night," wrote one. "Assimilation, and they don't do it."
Some used the incident to call for greater controls over who could come to Australia. "The immigration restriction act of 1901 was this countries greatest achievement."
Another man added: "At least the Aboriginals are getting left alone now ha oh well the Govt opened the doors for everyone to come here to freeload off the Lucky Country & it's free for all by the looks."
Other offensive posts included, "Shoot the C#### first then the dogs," and, "Shoot the lot of those African scumbags terrorising Melbourne."
Some of the messages were not overtly offensive or racist but supported the store owner's actions and the right to defend his business.
A typical response was: "Should he just fling open his doors and say help yourself? Obviously there's a hell of a lot more to this story than is here. He's been driven to this no doubt. The police have probably done little to nothing to help him."