A former county manager and All-Ireland winner punched another man during a row about Northern GAA teams.
Ross Carr (54) claimed the victim repeatedly insulted teams north of the border, calling them "Nordie knackers".
Carr was manager of the Down senior football team between 2006 and 2009 and won two All-Ireland titles with the county.
Judge Grainne O'Neill said she did not enjoy the "victim blaming" which it appeared Carr was endeavouring to do.
She ordered Carr to pay €5,000 compensation to the victim and imposed a three-month sentence, suspended for 12 months.
The defendant, of Main Street, Hilltown, Newry, Co Down, admitted before Dublin District Court to seriously assaulting Gordon Hunt at The Brazen Head, Lower Bridge Street, Dublin 8, on December 7, 2016.
Gda Conor McShane said Carr punched the victim in the face, leaving him with a fractured tooth and swelling to his upper lip.
Mr Hunt required root canal work, which cost €622. He told the court he had to wait for the swelling to reduce before the dental work could be done.
He described the experience as "less than fun".
Gda McShane said the men were with a group of sports journalists at a Christmas party and the assault took place after an argument over GAA.
The garda alleged the injured party made a number of insults to Northern GAA teams, including calling them "Nordie knackers". This was confirmed by independent witnesses.
His defence lawyer said Carr, a self-employed property manager, was married with five children and one grandchild.
Carr was heavily involved in Down GAA, both at under-age and senior levels, the court heard. The defendant apologised for his behaviour.