Amanda Marcotte has some thoughts on PUA ideology and Elliot Rodger.
This theory—that ordinary and worthy men are oppressed by women who refuse to have sex with them—was articulated in Rodger’s 141-page manifesto he sent to newspapers.
Women are incapable of having morals or thinking rationally. They are completely controlled by their depraved emotions and vile sexual impulses. Because of this, the men who do get to experience the pleasures of sex and the privilege of breeding are the men who women are sexually attracted to… the stupid, degenerate, obnoxious men. I have observed this all my life. The most beautiful of women choose to mate with the most brutal of men, instead of magnificent gentlemen like myself.
This sort of rhetoric is fairly common on some of the more embittered PUA forums, and the “men’s rights” forums that have quite a bit of overlap with them.
And it is what it is. It’s not all that belief-defying that one very warped guy would take the rage and channel it into violence. It’s surprising that more warped guys don’t. (But many of course do it one at a time, in private, without a manifesto.)