Knowing the patterns of reasoning associated with a genre can help you to structure your essay.
The second and most substantial part will likely break down into two sub-parts.
The logic is plain: if Hamlet's mother made a cuckold out of Hamlet's father, then all women are capable of doing the same and therefore share the blame.
The fact that Gertrude's hasty remarriage does not actually constitute adultery only underscores Hamlet's tendency to find in women faults that do not exist.
Though his rantings may be an act, they cannot hide his obsessive anger at one particular woman: his mother.
He counsels Ophelia to "marry a fool, for wise men know well enough what monsters you make of them" (139-41), thus blaming her in advance for the sin of adultery.