David Fletcher launched the attack on Ross Ottaway days after Mr Ottaway was accused of showing hardcore pornography to young children he had been babysitting.
Mr Ottaway, who worked as a bouncer, was reported to police on 16 April last year and is due to stand trial next month.
But days later, on 21 April, Mr Ottaway walked into a shop in Dundee’s South Road, where Mr Fletcher was working.
Mr Fletcher, who had been told of the allegations, ordered Mr Ottaway to get out of the shop.
When Mr Ottaway walked towards a drinks fridge where Mr Fletcher’s daughter was standing Mr Fletcher pushed him out of the store – before punching him twice in the face.
Mr Ottaway was left with horrific injuries to his eye with one of his eyeballs ruptured.
Fiscal depute Eilidh Robertson told Dundee Sheriff Court that Mr Ottaway had been left completely blind in that eye following the attack.
She said: “The accused shouted ‘you better get out of here’ when the complainer entered the shop. The complainer said I’m just here to get juice.
“The accused then went towards the complainer and pushed him towards the door of the shop. As he exited the complainer said ‘I never touched them’.
“The accused then punched him twice causing instant bleeding.
“He called police and friends as he left and was admitted for emergency surgery at Ninewells Hospital. A specialist registrar found the globe of his eye was ruptured and the contents of it was lost.
“The injury was described as extremely unusual. A repair to the surface of the eye was carried out and some of its contents were found on the surface.
“He has no perception of light in his right eye and has effectively been left blind in that eye.”
Mr Fletcher, 39, of Dundee, pleaded guilty on indictment to assaulting Mr Ottaway to his severe injury and permanent impairment at Lifestyle Grocers in South Road on 23 April 2013.
The plea was accepted on the basis that Mr Fletcher was under provocation at the time of the attack.
Andy Lyall, defending, said: “This was not some kind of drunken mindless thuggery that befalls some people. The accused took hold of him and shoved him to the door. That’s when this remark was made that he ‘never touched them’. He lost his temper and struck him. He bitterly regrets this but he lost his control.
“It was a perfect storm of a punch, an unfortunate blow. He has no training in boxing or martial arts, it was the most unfortunate punch in the world.”
Sheriff Tom Hughes placed Mr Fletcher on a community payback order with two years’ supervision and 200 hours unpaid work.
He said: “The consequences of this punch could not have been foreseen. It’s accepted you were acting under significant provocation at the time. You have shown remorse throughout.
“A custodial sentence would normally be almost inevitable but in this instance would not be in the public interest.”