It's a good point BUT the guys already have a physical advantage. The gun is an equalizer. All of a sudden, the guy COULD get hurt. So he'll think twice. He is a bully, after all.
Most bullies are cowards. That's why they pick on a smaller person. When that person fights back, even if the bully wins, he leaves the other person alone because he is at heart a coward.
When you ban guns, then the bullies have all the advantages because they don't need a gun in order to hurt a weaker person. And when you ban guns, criminals still somehow get them... because they don't care if they break the law. Meanwhile, places like Switzerland, which had mandatory gun ownership, also had extremely low crime rates.
Instead of banning guns, we should be teaching impulse control and ethics.
Until the 1970s, according to a buddy of mine from Louisiana, there were shooting clubs in rural high schools. Kids would bring their weapons to school and leave them in their vehicles. A friend of mine who was born in 1955 remembers walking down the street in Des Moines with a .22 rifle when he was 12 years old. They also used to take weapons on trains - there was an old I Love Lucy episode which showed this. The guy did need to show the conductor a permit for his gun, but that was it.
FYI, I'm actually a pacifist, personally. I have never owned a gun. But that is my CHOICE. I don't force my choices on others.