We live in a culture which almost completely ignores the experiences of boys. Puberty hits fast and young boys are thrown into a world that is literally saturated with the female sexual object and they are given very little guidance or tools to understand what they are going through.
This new and grand object of desire can do anything it wants. It can tease and flaunt, it can be used sexually and put on display, it can be bought for the price of lunch at McDonalds, but the boy isn't supposed to even really notice, isn't supposed to feel anything for it, and if and when he does, he is often rebuked, told that he is a pervert or he just needs to "learn to control it".
Most boys manage to stumble through it, often because they happen to be lucky enough to find someone who will stumble through it with them, but not all of them. Some are always on the outside. Some are alone in the dark.
People will for the most part just call Elliot names. An evil monster, or whatnot. They will focus on the anger and rage and violence, but the real root of the problem is pain. The unbearable and unmanageable pain of being completely isolated from the only thing one wants. That of course, doesn't excuse or justify what he ultimately did, but it is important to have a conversation about the root of the real problem. Not for his sake, but for the sake of all the other boys (and men) who are alone in the same darkness.
We do a relatively good job of understanding the pressures of society that impact girls and women (objectification, body image issues, eating disorders, etc), and rightfully talk about trying to eliminate said pressures without laying blame on those affected by it, but conversely we do a terrible job when it comes to boys.
Young boys, for instance who are exposed to pornography, we tend to just laugh off and say stupid crap like "boys will be boys," but if there is any part of Elliot's manifesto which should be read, I think it should be the part about his exposure to pornography and what it did to him. He was traumatized by it and that isn't something that he should have had to face.
As long as we continue to not have this conversation about the experiences of boys and we leave them alone in the dark, and don't give them tools and guidance to properly negotiate their reality, some of them will continue to resort to terrible means to try and close the gap between what they want and don't have.