It doesn't really matter what they did to them. It is not moral to return the same behavior.
He follows with the relationship of a person to the city. He says, "One must obey the commands of one's city and country, or persuade it as to the nature of justice. It is impious to bring violence to bear against your mother or father, it is much more so to use it against your country." (Crito 51c).
One should not only obey their father and mother, but more important the city. The city stands equal if not above the parents. We should understand that because the city was there before ones parents were born. Everyone has his or her ancestors who have a higher standard in life. However the city was there before them and so should be respected and laws should be followed.
Socrates explains his theory of the city and its rules as the nature of ones life. It is not moral to fight against it. We were welcomed to live in it and accept it how it is. .
A very important aspect of the city and its rules is that one is not forced to do as it dictates. One has the ability to choose between two options. You can either obey the city and its rules or not. If you want to go somewhere else you can do so, but do not complain here.
Regarding Socrates view one should not obey the law just because it is the law. As I said before you have two choices, but one of them is the moral option. We say that it is moral, as it was taught to us this way, but one doesn't really think about their own opinion in reference to it. .
We are absolutely commanded by our ancestors and the city. It is like being objects being commanded our whole life. Men have not the choice to decide what is moral for their standard of life. The moral way is what the city or their parents tell them to do. We are depending on their opinion to decide if we did wrong or not. On Socrates view it is not someone else's decision what is right or wrong, it isn't the moral life to follow others opinion about morality.