It's pretty simple really: the people that Socrates was “stinging”, specifically politicians, represented a dull-witted horse. Socrates was the fly that stung them with truth. read more
In Plato's Apology, Socrates says that his role is that of a gadfly (horsefly): "to sting people into a fury, in the service of truth", and to goad the 'steed' of state into awareness of its duties and obligations. read more
The questioning continues to Socrates being a harmful man to the society, Socrates replies as being part of the society he would be harming himself as well and no one would want to hurt themselves and even if he is, he should not be punished rather educated and shown the right way. read more