His target, Richard Gazzard, was a happily engaged co-director of Prestige Auto Traders in Rozelle. Kovacic falsely accused him of being a rapist and local police of covering up the crime.
The extraordinary tale of one man's blind jealousy was detailed by police when Kovacic stood trial in Central Local Court.
Prosecutor Sergeant Brad Scanlan told the magistrate, Gail Madgwick, that Kovacic, of Chiswick, could not handle the thought his now former girlfriend, Meje Tran, had kept in touch with Gazzard, who she had once dated.
Kovacic waged his hate campaign between 2004 and early 2006, distributing pamphlets with Mr Gazzard's photo under the heading "Buyer Beware" to letterboxes in the inner west.
His campaign came unstuck in an investigation that involved police retracing phone records and internet sites to Kovacic's home and work computers.
Kovacic pleaded not guilty to the charges, for which he faces up to five years' jail and fines of up to $5,500. But last Thursday Ms Madgwick found Kovacic guilty of two charges: using a carriage service to menace, harass and offend, and stalking with intent to cause fear, physical and mental harm.
In evidence at his trial last April, Sergeant Scanlan said the hate campaign began in April 2004, when Mr Gazzard received two anonymous calls from a man that were later traced to the home of Kovacic's father.
The caller told Mr Gazzard "you are f---ing dead. I know where you live" and later "I know where you work". By the end of the year, Kovacic had produced the first of three pamphlets.