Leon Kirk also spat in the face of two police officers while being detained and arrested, Wolverhampton Crown Court was told.
The husband and wife were confronted by a four-strong gang while checking what had happened after hearing the sound of breaking glass outside their home in Great Charles Street, Brownhills, on January 9.
The group, who had been drinking, came towards them while taking glass bottles from their pockets, shouted at them in “gang-style” language and started attacking the couple’s Vauxhall car, revealed Mr Patrick Sullivan, prosecuting.
They hurled a barrage of beer bottles and plant pots at the vehicle before kicking it.
Three of its windows were smashed, a wing mirror was torn off and the body work dented.
Then one of the group threw a bottle at the husband, cutting him above the eye and the 19-year-old defendant, who had not thrown the missile, walked up to him with arms spread wide and declared: “I am a boxer. I am a gypsy,” continued the prosecutor.
Unfortunately he had picked on a martial arts instructor who floored him but then Kirk punched the man’s wife in the face after struggling back to his feet and then ran away as the gang scattered.
Police called to the scene took the husband on a drive round the area during which he spotted Kirk who spat at the officers who carried out the arrest.
Kirk, from no fixed address, had a difficult upbringing which involved being taken into care but is now the father of a child and realises he has “a lot of growing up to do,” the court heard.
He pleaded guilty to damaging the car, assaulting the couple and two emergency workers while taking part in an affray and was given 21 months detention in a Young Offenders Institution by Judge James Burbidge QC.