The American pit bull terrier's owner Tyrone Spence has now been ordered to carry out unpaid work for having the dog, which was not stopped by electric shock shields giving out 40,000 volts.
The 24-year-old cried throughout the proceedings and asked the court if he could not be forced to litter-pick during his community order.
His defence solicitor Richard Quinn said: "He doesn't feel he should go around putting right what others have done wrong."
On the day of its death Spence's dog had already been given two sedatives by animal investigators – which didn't work – before suffering an allergic reaction after being sprayed with the fire extinguisher. Spence pleaded guilty to possession of the fighting dog, called Tyson, which was found at his previous address of Florence Avenue in Lanesfield, Wolverhampton, where tooth marks were discovered on the front door by Pc Summerfield of West Midlands Police.
Prosecutor Peter Love told Wolverhampton Magistrates Court: "Police had received information and found the dog inside.
"The dog made full contact with the electric shield and it apparently had no impact on him. The level of aggression shown was extremely high.
"In Pc Summerfield's opinion the dog would post a very real danger to the public if it was returned to Mr Spence. She couldn't exclude the potential for loss of life."
Mr Quinn said Spence, now of John Howell Drive in Tipton, was extremely upset about the loss of his dog.
He added: "The picture painted is not one my client recognises at all. It was completely placid and of no danger to the public."
Spence was found not guilty at Wolverhampton Magistrates' Court of a separate charge of failing to attend court and police bail, which he said was because he was not in the right frame of mind after his brother's three-year-old daughter had died of leukaemia.
He was given 60 hours' unpaid work and told to pay costs of £85.