A thug repeatedly kicked a man in the head in a row started over a beggar asking for money.
Luke Daley admitted to the attack in Huddersfield town centre in the early hours of April 29.
The 20-year-old has since been jailed for two years after pleading guilty to a spate of arsons.
Kirklees Magistrates’ Court was told that the victim, Carl Fleetwood, was walking along King Street with his girlfriend at 3.35am to get a taxi.
CCTV footage showed the couple becoming involved in a row with Daley, who suddenly attacked Mr Fleetwood.
Alex Bozman, prosecuting, said: “The footage showed Daley hitting him while he was on the ground.
“As the victim tried to get up he was kicked in the head three times.”
Magistrates heard that Mr Fleetwood suffered injuries including a cut bottom lip and soreness to his jaw.
Town centre CCTV operatives alerted police and directed them to Daley, of Ashenhurst Rise in Newsome.
He initially ran away but officers detained him and he admitted to the assault during his journey to the police station.
There he was found to be in possession of a small quantity of cannabis, an offence he also pleaded guilty to.
Daley said that he was stood next to a beggar who asked Mr Fleetwood for money.
His solicitor Mike Sisson-Pell explained: “The complainant became abusive towards the beggar and Mr Daley told him to shut up and mind his own business.
“The victim got to Mr Daley, threw a punch at him and ended up on the ground.
“He’s then hit the victim while he was on he ground. It’s a classic case of excessive self-defence.”
While Daley was on bail for this he was arrested for the more serious offences of arson.
He was seen in the early hours of February 16 torching three cars at random parked on Kingsmill Lane in Newsome.
A witness saw him leaning through a Renault Megane, setting fire to the seats with a lighter and then doing the same with a Suzuki Swift and Toyota Aygo.
Last Friday he appeared at Leeds Crown Court and pleaded guilty to three counts of arson.
A judge sentenced him to two years in a young offenders’ institution.
Daley appeared for the hearing in Huddersfield via a video link from the Doncaster prison.
Mr Sisson-Pell added: “He’s already improved massively in prison.
“He was drinking far too much, he had a real alcohol problem, and because of his incarceration he’s dealt with that.
“He’s getting qualifications and is a very positive and changed young man to the person I saw some weeks ago.”
Magistrates sentenced him to six weeks in custody, to be served concurrently and so will not extend his existing sentence.
He will have to pay £115 victim surcharge upon his release and the cannabis will be forfeited and destroyed.