The former vice-president of Fifa has warned controversial footballer James McClean that the time has come to stop mixing sport and politics.
But Jim Boyce also condemned the fans who subjected the Londonderry-born Republic of Ireland international to a barrage of abuse during West Brom's Premier League match with Manchester City on Monday night.
New West Brom signing McClean found himself in the unusual situation of being jeered by a section of his own club's supporters during his competitive debut for the Midlands team.
The barracking is understood to be a legacy of 26-year-old McClean's refusal to face the Cross of St George flag during a pre-season friendly in the United States.
"That sort of abuse is unacceptable," said Mr Boyce, who retired from world football's governing body earlier this year.
"Normally, fans tend to jeer their own player if he's not working hard enough, or wants a transfer, but this is different.
"James McClean is a talented footballer, but he needs to be a lot more careful about the way he reacts to situations.
"With him, it isn't a case of there being a one-off, high-profile incident. There have been several of them."
He added: "Sport and politics should never mix.
"James has his own principles but he has to concentrate on his game, realise he's earning a good living in English football and hopefully there'll be no more incidents.
"Human nature being what it is, people will react to these things.
McClean, who played for Northern Ireland at several levels before opting for the Republic, was removed from the action halfway through the 3-0 defeat by City. Prior to the flag incident in Charleston, South Carolina, some West brom fans had voiced their concerns about the club signing McClean because of his refusal to wear a Remembrance Day poppy at his previous clubs Wigan and Sunderland. In an open letter to fans last year, he explained this was due to events such as Bloody Sunday.
McClean courted further controversy recently by tweeting his views on the ongoing Derry/Londonderry name debate - the day after a rival player had received a record 10-match ban for directing sectarian abuse at the winger.
Linfield manager Warren Feeney has said football supporters should get behind their players, but are entitled to boo if those players aren't performing. "With the James McClean situation it's a difficult one because he's got his beliefs and fans will have theirs," he said.
"At the end of the day it's a football match and he's out there to play for West Brom. I'm sure he needs the support but you can't tell what fans are going to do."
Sky Sports veteran Alan Parry, meanwhile, has been accused of 'trolling' McClean by referring to him as "the Northern Irishman from Londonderry" during his live commentary of the game.
It provoked a backlash on social media, with many siding with the player.
Frankie Harkin wrote on Twitter: "Alan Parry should apologise for his provocative statement tonight... a clear dig at McClean.
Limerick journalist Alan Morrisey, meanwhile, asked: "Has Alan Parry referred to Raheem Sterling as the Jamaican from Kingston yet?"
Daniel Collins wrote: "Insidious #AlanParry can hang head in shame. Obnoxious trolling of #JamesMcClean, a member of Derry's nationalist community."
Others took Parry's side, with Jason Connolly asking: "What's wrong with him stating fact or did I miss something?"
McClean's stance on the English flag was recently defended by Daily Telegraph columnist Jonathan Liew, who wrote: "The criticism essentially runs thus: if McClean is content to earn a living in Britain, why does he hate it so much? Why not go back to where he came from (which, we should probably point out, is technically also Britain)?
"This idea that earning a living from a country should entail tolerance for its customs and rituals remains surprisingly tenacious, if inconsistently applied.
"At what stage, for example, should the Chinese and Russian investors buying up large swathes of London be informed about the ancient British tradition houses are lived in, rather than left empty and used as investment vehicles?
"Instead, McClean's lack of reverence is singled out, largely by the same people who thought Gazza pretending to play the flute during the Old Firm derby was absolutely hilarious. In 1938 the England team famously performed the Nazi salute whilst playing in Berlin.
"And the irony is, had one of the players dissented and turned his back on the swastika, he would now be hailed as a principled hero."