George Thomson (50), shouted and swore at the other motorist who was using the forecourt tyre inflator.
The commotion was heard by other motorists and the kiosk attendant, and police were called.
The incident happened at Morrisons’ supermarket petrol station in Stirling on July 23 last year the city’s sheriff court was told.
Thomson, a £35,000-a-year ScotRail manager, of Redding Road, Westquarter, denied using threatening and and abusive behaviour.
Emergency Services Day: 999 crews take over Falkirk High Street
Falkirk 80s rockers reform to play first gig in 36 years
Bosses confirm Falkirk shoe shop closure
Rosebank: 31 Year Old Lowland single malt from original Falkirk distillery casks on sale for £1800
Resurfacing work leads to road closures in Grangemouth
His mother Isobel Thomson (78), said in evidence that the other driver had remained at the air pump for “four or five minutes” after completing the inflation of his four tyres.
But she insisted: “Our George was cool as a cucumber about it.”
Sheriff Gillian Wade QC found Thomson guilty of the offence, which she also found was racially-aggravated, after a brief summary trial.
She fined him £600 and told him: “It’s quite clear that frustration got the better of you.”