Celtic manager Neil Lennon has praised skipper Scott Brown for handling a "horrendous" situation outside Ibrox.
Brown was taunted over the death of his sister Fiona, who died from skin cancer in 2008, while boarding the team bus following Celtic's 2-0 win over Rangers earlier this month.
A 15-year-old boy has been charged in connection with the incident, which was captured on video.
Rangers issued a life ban and apologised to Brown, who stopped in his tracks when he heard the comment but did not respond.
Lennon said: "I've had a brief chat with him about it and I think he handled the situation very well.
"It's incredibly hard (not to react). I don't know what I would have done. I'm older now and Scott is a lot more mature. Maybe five or six years ago it might have been a different outcome.
"I'm not sure what that lad was trying to prove or what his thought process was, if he had one at all. It's disgusting.
"I think it's awful, horrendous. To even think about that, let alone say it, is horrendous.
"I applaud Rangers for the swift action they took and the support a lot of their fans have given to Scott but it's got to stop. There's no call for that.
"We're talking not only here, in Britain now there seems to be this uprising in a lot of racism again. It's rearing its ugly head.
"We have a sectarian problem here, we know that.
"Ninety five per cent of supporters are really good and, like Scott said, he doesn't mind during the game, but when we're out and about on the streets trying to live our lives, we are not in a football ground. They have no right to abuse or insult people in that manner."
Brown pinpointed social media as a platform that has allowed extreme comments to spiral, and Lennon agreed.
"It sometimes makes young ones think that it's all right," he said. "It's not.
"Again we have people in authority and players of the highest calibre asking social media networks to clamp down on it. It has to stop.
"There's no accountability or responsibility for these individuals."