The FA is set to investigate scenes at Sunday's derby games as a smoke bomb and flare were released at the Birmingham derby and 24 arrests were made relating to the Wear-Tyne derby.
Many of the headlines on Monday surrounded the incident at the end of the 1-1 draw at Sunderland as a Black Cats fan was able to get onto the field to confront Harper.
"All I saw was Steve Harper on the floor," Bruce said. "I didn't know what had happened at the time.
"I would like say a 'well done' to the Sunderland fans who gave the kid up - and he is a kid, that's what I can't understand either, the age of the lad - but the Sunderland fans gave him up, and rightly so. He's in police custody as we speak.
"The one thing we are up here, we love the football and the passion and all the rest of it, but you don't need to see any scenes like that. I hope they ban the kid for a long, long time because he deserves it.
"When I saw the age of him, I just really can't understand society today. What goes through his mind when we have just scored with a minute to go? Why the hell he has got to come on to the pitch and confront Steve Harper baffles me.
"When you see the age of this young kid, it is quite remarkable how has got that in his mind, to run on to the pitch. Why don't you just celebrate with 50-odd thousand like everybody else did?
"Unfortunately, it is a sad indictment of where we are with the youth of today. He's a kid. It's ridiculous."
Newcastle boss Alan Pardew, though, played down the incident.
"Harps said he barged him in the back," he said. "At first sight, it looked an ugly incident, but I don't think it was that bad. There was no punch thrown."
Nonetheless, Northumbria Police confirmed 24 arrests had been made relating to the game. Offences included drunk and disorderly, disorderly conduct and going into the playing area, while reports have suggested bottles and ripped-up seats were thrown.
The match commander, temporary Chief Superintendent Steve Neill, said: "The crowd was mainly good natured and the overwhelming majority wanted nothing more than to enjoy the action on the pitch in an atmosphere free from violence and disorder.
"However, there were still some troublemakers who were determined to spoil things for the genuine fans. We had anticipated the potential for disorder and had the resources in place to deal with it swiftly and firmly.
"The policing operation went well and I would like to commend the actions and professionalism of all the officers involved who managed to diffuse a number of difficult situations.
"I would also like to thank the stewards for their assistance."
On Monday, an FA spokesman said: "We are awaiting reports [from the Wear-Tyne derby] this morning and will be proceeding from there."
A Sunderland statement added: "The vast majority of fans in the 48,000 capacity crowd behaved very well and we thank them for their loyal support.
"Sunderland AFC operates a zero-tolerance policy towards anti-social behaviour of any kind within the Stadium of Light, and we are proud of our reputation as a family club.
"Working closely with Northumbria Police, we will ensure that appropriate action is taken against anyone found to have been involved in any such behaviour at yesterday's game.
"The club also recognises the positive role Sunderland supporters played in helping to identify the small minority responsible for anti-social behaviour to stewards and the police."
The Birmingham derby was attended by a limited number of fans - 22,000 - as capacity was reduced due to trouble between the Blues and Aston Villa fans during their Carling Cup tie last month.