Why tyranny arises from Democracy (Plato)

How so? When a democracy which is thirsting for freedom has evil cupbearers presiding over the feast, and has drunk too deeply of the strong wine of freedom, then, unless her rulers are very amenable and give a plentiful draught, she calls them to account and punishes them, and says that they are cursed oligarchs.
Yes, he replied, a very common occurrence.
Yes, I said; and loyal citizens are insultingly termed by her slaves who hug their chains and men of naught; she would have subjects who are like rulers, and rulers who are like subjects: these are men after her own heart, whom she praises and honours both in private and public. Now, in such a State, can liberty have any limit?
Certainly not.
By degrees the anarchy finds a way into private houses, and ends by getting among the animals and infecting them.
How do you mean?
I mean that the father grows accustomed to descend to the level of his sons and to fear them, and the son is on a level with his father, he having no respect or reverence for either of his parents; and this is his freedom, and metic is equal with the citizen and the citizen with the metic, and the stranger is quite as good as either.
Yes, he said, that is the way.
And these are not the only evils, I said --there are several lesser ones: In such a state of society the master fears and flatters his scholars, and the scholars despise their masters and tutors; young and old are all alike; and the young man is on a level with the old, and is ready to compete with him in word or deed; and old men condescend to the young and are full of pleasantry and gaiety; they are loth to be thought morose and authoritative, and therefore they adopt the manners of the young.
Quite true, he said.
The last extreme of popular liberty is when the slave bought with money, whether male or female, is just as free as his or her purchaser; nor must I forget to tell of the liberty and equality of the two sexes in relation to each other.
Why not, as Aeschylus says, utter the word which rises to our lips?
That is what I am doing, I replied; and I must add that no one who does not know would believe, how much greater is the liberty which the animals who are under the dominion of man have in a democracy than in any other State: for truly, the she-dogs, as the proverb says, are as good as their she-mistresses, and the horses and asses have a way of marching along with all the rights and dignities of freemen; and they will run at anybody who comes in their way if he does not leave the road clear for them: and all things are just ready to burst with liberty.
When I take a country walk, he said, I often experience what you describe. You and I have dreamed the same thing.
And above all, I said, and as the result of all, see how sensitive the citizens become; they chafe impatiently at the least touch of authority and at length, as you know, they cease to care even for the laws, written or unwritten; they will have no one over them.
Yes, he said, I know it too well.
Such, my friend, I said, is the fair and glorious beginning out of which springs tyranny.
Glorious indeed, he said. But what is the next step?
The ruin of oligarchy is the ruin of democracy; the same disease magnified and intensified by liberty overmasters democracy --the truth being that the excessive increase of anything often causes a reaction in the opposite direction; and this is the case not only in the seasons and in vegetable and animal life, but above all in forms of government.
True.
The excess of liberty, whether in States or individuals, seems only to pass into excess of slavery.
Yes, the natural order.
And so tyranny naturally arises out of democracy, and the most aggravated form of tyranny and slavery out of the most extreme form of liberty?