Craig Walker, 30, was furious after Ashley Wilson let go of a door he had been holding at the Vue Cinema complex in Hamilton, Lanarkshire, as he made his way out.
Mr Wilson believed Walker was taking too long to come out of the door and decided to walk away but was attacked outside.
He was called an 'English b*****d' and a 'w****r' before being pinned him to the wall by a drunk Walker who then ripped his headphones out.
A terrified Mr Wilson, who has a disability with his left arm, was then punched to the face which knocked him to the ground.
He eventually managed to flee to a nearby supermarket while Walker, who had been out celebrating his 30th birthday, walked away.
A court heard Walker was so drunk that he cannot remember anything about the attack.
Walker has now appeared at Hamilton Sheriff Court and admitted assaulting Mr Wilson in October last year.
He has been jailed by Sheriff Alasdair MacFadyen who told him he would have caged him for 27 months had he not pled guilty.
Depute fiscal Mairi-Clare McMillan said: "The witness Wilson had attended the cinema in Hamilton to see a film and at 00.30 on the 8th of October he proceeded to exit the cinema and noticed that the main exit was locked and that it was a side door that was open.
"He proceeded to exit the locus and at this time he was on his phone to his friend.
"As he was leaving he observed the accused attempting to leave via the locked door and shouted to inform him of what door he had to use.
"He thereafter held the door open for the accused but due to the time it was taking for the accused to get over, he let go of the door and made his way outside.
"He was still on his phone when the accused began shouting and swearing towards him shouting 'English b*****d' and 'w****r'.
"The accused then took issue with the fact that the witness was on his phone and pushed him back against a door.
"He then ripped his headphones from his ears while shouting at him and then grabbed him by the scarf pulling him about while producing a fist with his right hand."
Miss McMillan added: "The witness felt terrified because he was holding his phone and had a disability problem with his left arm.
"The accused then assaulted him further by punching him to the face causing him to fall to the ground.
"The witness managed to get to his feet and walk to a nearby Asda and the accused also walked away at that point."
Marisa Borland, defending, said: "It had been his birthday two days before and he intended enjoying a quiet birthday weekend but under peer influence found himself misusing alcohol.
"He can recall nothing about his offending behaviour and that is frightening to him and he fully accepts the narrative provided today and by the complainer.
"He has shown remorse to me about this.
"He has indicated that he wishes the court to just proceed to a custodial sentence."
Sheriff MacFadyen said: "This was an unprovoked assault on a stranger whose only crime was being in the wrong place at the wrong time coming out of the cinema.
"I'm told you had consumed alcohol which is no excuse and in fact makes matters worse.
"You have an extensive record which discloses convictions of violence, disorderly behaviour and breaches of bail and you have committed this horrible crime despite positive assistance from a charity.
"Custody is clearly the only appropriate disposal."