Socrates did not plea for a lesser charge because he felt a just sentence was not possible as he was not guilty.
As Plato writes in his dialogue of hearing, Socrates states, “Since I am convinced that I wrong no one, I am not likely to wrong myself.” Therefore, he would have had to play on their emotions, like the Sophist, and would have been guilty, but chose to speak the truth. His opinion on exile was that it would ultimately end in the same conclusion as this trial, as wherever they sent him he would still talk to anyone and do as the gods commanded him to
do.
Socrates refers to himself as a "gadfly" which is what we would call a “horsefly”. It worries horses and other animals and keeps them from resting. The animals use their tails to try, and swat them away. He felt that he had that same effect on the city, and its occupants. He was constantly questioning them and trying to find out answers, much to their displeasure. Socrates made them doubt their idea and beliefs; this confused them and made them angry. Overtime this created resentment and was one of the reasons he now faced criminal charges. This was their way of “swatting” at him.
In W.T. Jones writings, he says the difference between the older & younger generation of Sophists was they were “radical.” The earlier Sophist were more conservative and Cautious-minded than the newer. The younger started questioning whether the law was reality or just convention. Since it was not matter you could see or touch then it is what man makes it, and why should we adhere to something that does not benefit us but the men who are in charge of making the laws. The older Sophist felt that operating under the law was to their advantage but the younger were more radical, and felt if it was not to their individual advantage it had no place in their society. If you felt it was pleasing then do it if not then do not. In the end, they felt that power or force was what mattered in the world.