Stephanie McKay, from Pudsey, was waiting at Pudsey Bus Station with her three children on Friday night as there were no buses.
As she made a phone call to arrange a lift home, she says she saw an elderly man walk over in her son's direction.
Ms McKay says the man walked straight into her three-year-old son, tripping him with a walking stick and sending him flying to floor.
She added: "Out of courtesy I asked my son to apologise if he caused any inconvenience.
"But the man launched a verbal attack on me saying I was controlling him. As we were not in the wrong, a lot of the people in the bus station then all started shouting at him and calling him a disgrace, and asking why he would do that to a child."
Ms Mckay said although her son was not left badly hurt, he complained of his head and legs hurting and was too shaken to get back on a bus.
She said: "A lovely member of public stood up for my three-year-old and checked he was okay. They gave him some sweets, as he was so distraught about what happened.
"I've since been told this man is quite well known for his hatred of children."
Ms McKay has reported the incident to the police. Anyone with information is asked to contact 101 quoting crime reference number 13190613599.