Children as young as four in the Boys' Brigade were shouted at in a "sectarian" manner, furious parents said.
Around 40 young people left St John's Church in west Belfast on Sunday and embarked on their 200-yard parade for their Enrollment Service.
But claims that they were shouted at and cursed at by "grown men" has sparked public outcry on social media, reports Belfast Live .
And Vicky Lavery fears for her son's future, after the five-year-old was left distraught.
She said: "My son has known nothing of any form of hate in his life, and now he is asking why the men were angry with him.
"And today, he is refusing to even speak about it. Grown men were rolling their windows down and shouting at out at the kids.
"One man shouted 'hang yourselves with your Union Jacks,' it was awful. I really hope that this doesn't affect him when we go to that bus stop again where it happened. I want a better future for him than this sort of behaviour.
"I take him everywhere and try to make sure he is in groups with children from all types of backgrounds. We are not a narrow minded families and don't care about race or religion.
"Parents are just outraged after this. Personally, I take a person at face value no matter where they are from or their background. We are meant to be moving forward but how can we if men in their 50s are still stuck in the 1970s?"
Brian Kingston, DUP councillor, said that he was "disgusted to hear of the sectarian abuse" and that he is looking into the incident.
He said: "This is appalling intolerance and sectarian hate crime directed at children. I am disgusted to hear of the sectarian abuse directed at members of 17th Belfast Boys Brigade Company as they paraded from their annual Enrolment Service at St John's Church of Ireland, Upper Falls.
"Around 26 Primary School age boys, 10 Secondary School age boys accompanied by their BB band and 10 adult officers, were parading the short distance to where most of the members live.
"To the car drivers who blared their horns continuously at the BB company, to the man at the bus stop who shouted prolonged abuse at the Company members, including sectarian abuse and 'go hang yourself on your Union Jack', to the car passengers who also shouted sectarian abuse, they are a disgrace and should be ashamed of themselves.
"I will be speaking to senior PSNI officers on the police response and how the main perpetrator was able to leave the scene on a Glider bus despite police officers being present at the scene."
A PSNI spokesman told Belfast Live that they accompanied the parade on Sunday morning.
Chief Inspector Gary Reid said: "As local officers accompanied a parade on Sunday travelling along the Stewartstown Road, a car overtook the parade.
"Police promptly stopped the vehicle and spoke the driver who apologised and was given advice and guidance about their driving
"Later, as the parade returned along the Stewartstown Road, a number of people became involved in a verbal altercation.
"Local police officers immediately intervened and spoke with a number of people about their behaviour, which calmed the situation and the parade continued on its journey."
