This story is set around 1730, prior to the outbreak of the Revolutionary War, between the American colonists and the British Crown.
The world Hawthorne imagines is one free of the constraints placed upon the colonial people. This would have included taxes on daily necessities like sugar, tea, tobacco, etc. (The high and wide-reaching taxation was in place to help England pay for debts incurred during the French and Indian (Seven Years) War.)
As time passed, and more and more things were taxed, the colonists became more frustrated and enraged. This would have been the motivation behind the hate expressed to Robin at the mention of his uncle's name. This would also explain the appearance of Major Molineaux, tarred and feathered, on his way out of town in the hands of an angry mob.
Robin has come to know that the world is so much larger than he had imagined. First, he is obviously unaware of the political climate in the colonies, perhaps because he is from an outlying location.
However, he is also caught up in his own perceptions of the world because of his isolation: when the people he meets become angry at the mention of his uncle's name, he excuses their behavior, blaming it on their country manners or his lack of money.
His naivete is obvious when the prostitute (woman in scarlet petticoat) tries to lure him into her house, and once again when he sees his uncle's ill-treatment, and laughs along with the rest of the crowd, louder than they perhaps because he doesn't know how else to respond.
Perceiving that everyone he has met since arriving in the city may be Robin's epiphany of what he did not know of the world, and now what he does know after seeing his uncle.
When Robin tries to leave town, the man he met in the crowd will not give him directions, believing that even without his uncle's help, Robin can still make a life for himself in the city.
Perhaps Robin is learning that knowledge of the world changes you, and you can never go back, but must make do with what you have to work with.