Self-proclaimed unionist activist, Jamie Bryson, mistook the flag of Munster for the image of a man wearing a balaclava during the game between the Republic of Ireland and Northern Ireland in Dublin on Thursday.
Bryson took the image of an Irish tricolour draped over one of the stands inside the Aviva Stadium and circled what he thought was a "masked terrorist".
"So, during an evening of anti-British hate and abuse from Republic of Ireland supporters, they also unveil a banner of a masked terrorist. This is the country Theresa May wants to de facto rule over N.Ireland," Bryson tweeted to his 16,900 followers on Twitter.
Bryson's tweet soon backfired when people from both sides of the political divide pointed out that what he had actually done was mistake the flag of Munster for a man wearing a balaclava.
Bryson deleted the message soon after and to his credit, he admitted he got it wrong.
"We all make mistakes, if you can throw the hands up and laugh at yourself when you get it wrong, then there’s no point being on social media," wrote Bryson.
"Good for the goose, good for the gander!," he added.
The match between to the two teams ended a scoreless draw.