For an increasing number of people, the only socialization they do is on-line. They have no friends, no girlfriends, only co-workers. The only sexual release they have is from pornography, the vast amounts of it give them the false impression that making porn is something every woman participates in. In short, they think all women have sex upon request with anyone who asks and for any reason and when these men aren't having sex, they're bewildered and angry.
So while people focus on the sex aspect of this, it’s part of a larger problem of social isolation of too many people.