You shouldn't hate others.
Norm is at the bar and a stranger accidentally spilled Norm's beer.
Norm wants a new beer.
Norm tells the stranger not to worry about it because mistakes happen and the stranger insists on buying Norm another round.
Norm insists that the stranger buy him a new beer and forever holds the mistake against him.
The stranger has a good night getting to know Norm as they buy beers for one another.
The stranger feels bad but then angry when Norm remains hostile which leads to a bar fight.