How we cite our quotes: (Day.Story.Page)
Quote #1
For to the eternal shame of those who nowadays lay claim, despite their corrupt and disgraceful habits, to the title and distinction of lords and gentlemen, our modern courtiers are better described as asses, brought up, not in any court, but on the dungheap of all the scum of the earth's iniquities. In former times, their function usually consisted, and all their efforts were expended, in making peace whenever disputes or conflicts arose between two nobles [...] (I.8.60, Lauretta's story of Guglielmo Borsiere and Ermino Skinflint)
Lauretta is indulging in a bit of a "those were the good old days" rant. It's true that in every age there's a sense of decline and decay of breeding and manners, but this probably more of a problem during the plague years, where it would be useful to have a generous and well-functioning upper class to try to keep society from falling apart. Her strong and colorful language isn't typical of what we've heard so far in the brigata's conversations.
Quote #2
It is therefore right and proper that before an impartial judge, people of different social rank should not be punished equally for committing an identical sin. For nobody would, I think, deny that if a member of the poorer classes, obliged to earn a living through manual toil, were to surrender blindly to the promptings of love, he or she would be far more culpable than a rich and leisured lady who lacked none of the necessary means to gratify her tiniest whim (II.8.150, Elissa's story of Walter, Count of Antwerp. The King of France's daughter-in-law is about to proposition of him).
Here's some Orwellian reasoning for you: the rich can't be blamed for their sexual indiscretions, because all that free time with nothing to do…well, you get to thinking about love and, you know…it's inevitable. On the other hand, if you're working all day, you have no such excuse. This sounds a little like those members of the 1% who are always insisting that they're the real victims.
Quote #3
'You clearly fail to realize that in this respect, your strictures should be aimed, not at me, but at Fortune, who frequently raises the unworthy to positions of eminence and leaves the worthiest in low estate […].Consider each of your nobles in turn, compare their lives, their customs and their manners, with those of Guiscardo, and if you judge the matter impartially, you will conclude that he alone is a patrician whilst all those nobles of yours are plebeians.' (IV.1.297-298, Ghismonda speaking to her father about her lover)
Ghismonda's trying to keep herself and her lover alive by arguing with her father, who's objecting to her getting involved with a guy with a lower social status. She's got a couple of counterarguments. First, it's merit that counts, not heredity; and second, the social class you're born into is all a matter of luck. Boccaccio would seem to agree. His stories include heroes and villains from all walks of life and social classes.