Hamlet is a perv. Really. Oh, not the kind of perv who goes around doing gross stuff—as far as we can tell, Hamlet isn't actually interested in girls at all—but the kind who just can't stop thinking about other people's sex lives. Including (especially) his mom's. The young prince is disgusted by his aging mother's sexual appetite, which eventually becomes the way he feels about all women in general. According to Hamlet, female sexuality makes the entire world seem like an "unweeded garden: in other words, it's associated with deception, sin, and a fallen world. No wonder he can't lay off the dirty jokes.
Hamlet's suicidal disgust with the world has more to do with his mother's sexual betrayal of his father than Claudius's murder of his father.
Hamlet's view that all women are "breeders of sinners" not only reveals a sexist attitude but also suggest that Hamlet (a "sinner") finds himself to be just as revolting as the corrupt world around him.