The message was posted in the wake of a number of tweets following a match between Hearts and Celtic last year.
And in court at Dumfries this week, David Vivers, 23, of Drummond Road, Annan, admitted sending the message last December accusing the player of being a member of a proscribed terrorist organisation.
Other Twitter users had contacted police and they traced Vivers.
Solicitor Gavin Orr said that Vivers had lost his job as a result and now realised how stupid he had been.
He had no interest in Irish politics or religion and simply had been drunk and annoyed.
Vivers was fined £300.