The 49-year-old, from Glasgow, has learning disabilities and was badly affected by the incident on a journey from Parkhead to his home in Easterhouse. After a few weeks he realised he needed to speak up about it to help others.
"Nobody came to my aid. The bus was full but nobody helped me," he recalled. "One of the girls called me all the names under the sun and pushed me up against the window while her two friends thought it was a great laugh.
"After that day I closed myself off for four weeks, but then I knew I had to do something about it. If I had given up, those who make fun of people with a learning disability would have won."
His positive action is now helping those with learning disabilities and educating others.
He saw an advert at the Bridge Group, Easterhouse, about a company, Diversity Films, running a film school and joined up to make a film about the effects of bullying.
With the help of Brace, a club for adults with learning disabilities, he got his project off the ground. The result was My Life, which premiered at the Bridge Group in 2009 and was quickly followed by My Life 2, which was shown at the Scottish Parliament.
He said: "I have had a lot of positive feedback about the films from people I did not even know. It helped them to go and get help after something similar happened."
Peter's campaigning work has not stopped there. He has now persuaded FirstBus to use the film as a training tool for drivers.
A member of Enable Scotland, Peter is an ambassador for the charity that works for people with learning disabilities.
Enable, supported by this year's Herald Christmas Appeal, campaigns to ensure people with learning disabilities are valued equally, listened to and included. It wants everyone to have the same opportunity to achieve the things they want out of life and works to change the law and challenge prejudice.
Peter works at Silver Birch (Scotland) garden centre in Milton Of Campsie, Dunbartonshire, and Cardinal Winning School for children with special needs in Tollcross, Glasgow.
He also attends a local writers' group and is involved with Enable Scotland's HUBS campaign to improve services for disabled people on trains.
What spurs him on is the wish to help others. He added: "If others can begin to understand the difficulties we face and how we try to deal with them, life can be better for all in the community."