This is a great question. A little historical context is important to understand these words. First, Sophocles is writing from the point of view of an Athenian citizen. Athens, of all the cities, of the Greek world was the most democratic. All adult men in the city (polis) had political right, responsibilities, and power. They served as jurors, soldiers, and could even hold office. It was a huge social experiment, since it was the first democracy in the West.
Within this context, Haimon is expressing a belief in a democratic system. More specifically, he is against the opposite of democracy, which is tyranny.
With that said, it is important to underline that not all Greek cities held this view. Some cities had oligarchies in place and other cities did have tyrants or kings.
Sounds like Haimon was voicing the Greek belief in democracy where the people are given the freedom to not only choose their leaders but voice their opinions more openly. This speaks against the idea or thought of a dictatorship where all the decisions are made by a single individual. I think Haimon is trying to say that a city cannot be effective if only a single voice is heard and is making all the decisions.