How does Dickens present the French upper classes in the run-up to the French Revolution in A Tale of Two Cities?

Dickens's portrayal of the French aristocracy is far from flattering. He laments the great poverty, injustice and exploitation that existed in France during the ancien régime. Despite this, Dickens was profoundly hostile to the violence and social upheaval caused by the French Revolution. This is explicitly shown throughout A Tale of Two Cities. Nonetheless, Dickens still has enormous sympathy with the condition of those who felt they had nothing to lose and proceeded to turn the country upside-down. But what he won't tolerate is one form of violent repression being replaced by another. And he's incredibly anxious to avoid the same thing happening in England. Indeed, one of the running themes of A Tale of Two Cities is the enormous contrast between the relative peace and stability of England and the bloody chaos of Revolutionary France.
Dickens has no time for the French aristocracy and makes it abundantly clear that they have contributed significantly to their own downfall. The heartless Marquis St. Evrémonde is a perfect symbol of how Dickens looks upon the Second Estate, with its sneering indifference and contempt for the common people. When his carriage runs over a little boy in the street, St. Evrémonde shows more concern for his horses than for the poor broken child. He regards the peasantry as "vulgar" and would happily run over any number of these "dogs" to exterminate them.
However, St. Evrémonde's nephew, Charles Darnay, is a much more enlightened member of the French upper class. He strongly rejects his wicked uncle's cruel contempt for the peasantry and supports efforts to ameliorate their wretched poverty. But it's telling that Charles can only really do this when he has formally renounced his title. The implication is that the French aristocracy is irredeemably decadent and heading toward an inevitable, and richly deserved, demise.