Mr Oyston sued Stephen Reed over material posted on a fans' webzine, Back Henry Street, in June 2015.
Mr Justice Langstaff in the High Court in Manchester ruled Mr Oyston was blameless and Mr Reed's allegation was untrue.
The verdict comes the day after the club was relegated to League Two.
Mr Reed's website posting claimed the club chairman entered into a foul-mouthed rant at him in public, held a gun in such a way as to make Mr Reed believe he was about to be shot at and had assaulted Mr Reed and put him in fear for his safety or even his life.
The judge said judgment for Mr Oyston was entered in August 2015 and Mr Reed now accepted the club chairman did not brandish a gun at Mr Reed, who maintained had not lied about the incident since he had given his honest opinion.
In ruling Mr Oyston was blameless, the judge added that further libel had not been discouraged by an award in an earlier action brought by Mr Oyston against another supporter, David Ragozzino.
The judge said the effect appeared to have been "to stir up, and maintain, resentment of and hostility" toward Mr Oyston and his wife Victoria.
He ordered Mr Reed to pay Mr Oyston £30,000 and his legal costs.
Mr Reed was among a number of Blackpool supporters unhappy about the way the Oyston family have run the football club.
Fans have held regular protests and boycotted games over the past two seasons.
Mr Oyston was fined £40,000 in June and banned from football activity for six weeks by the Football Association for five breaches of aggravated misconduct after sending abusive and insulting text messages to a fan.

A panel of judges compiled a list of the country's 100 most influential females for Radio 4's Woman's Hour.
Further down were author JK Rowling at seventh and Scottish Deputy First Minister Nicola Sturgeon at 20th.
One judge, journalist Eve Pollard, said the list highlighted the sectors where women were still under-represented.
The Queen's granddaughter-in-law, the Duchess of Cambridge, did not make the list but the judges noted her potential to do so.
Ms Pollard said: "Most women on our list were judged to have power because they had reached a place where they have control - of policy, of direction, of influence, of staff.
"The panel, a democratic group, also felt that we should include some women who have what we describe as soft power - not hire and fire or innovative financial decisions but the ability to transform the way we think about ourselves.
"Inevitably, not everyone will agree with the 100 we have chosen. There are some omissions. For example, we had long debates about the Duchess of Cambridge. Is she influential? Hugely. Is she powerful? Not yet.
"What this list does is shine a light on those sectors where too few women are getting to the top, like politics, FTSE companies, the military and journalism.
"Our legacy, we hope, is that this list might change that."
David Cameron's speechwriter Clare Foges, singer Adele and broadcaster Clare Balding were among those outside the top 20 but on the full list.
The judging panel also included Conservative MP Priti Patel, Labour peer Oona King and crime novelist Val McDermid.
Figures compiled by the BBC News website last year showed fewer than a third of the UK's most influential jobs were held by women.
Women occupied on average 30.9% of the most senior positions across 11 key sectors analysed, including business, politics, the judiciary and policing.
Campaigners said progress was still too slow.
The top 20 names in the Woman's Hour list are:
More information about the Women's Hour Power List can be found here.
Blackpool Football Club's chairman Karl Oyston has won £30,000 in libel damages from an abusive fan who claimed Mr Oyston threatened him with a shotgun.
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The Queen, Home Secretary Theresa May and Santander bank boss Ana Botin have been declared the UK's top three most powerful women in a BBC survey.