It is always possible to identify in some way with reprehensible people. Hitler loved dogs. Jeffrey Dahmer loved his grandmother. It's a cliché. There is nothing profound about reading a manifesto like this guy's, or the Unabomber's, or Anders Breivik's, and seeing in there some small reflection of your own psyche. It is normal to have had dark thoughts at some point in your life. The question is how deep, how often, and for how long these thoughts last past your teens.
I don't begrudge anyone for having these thoughts. But I do question why they are being shared in this thread, at this time, and so persistently.
A number of people will have identified in some way with the killer, and that's not necessarily evil. But that wasn't everyone's instinct. There are many people who, on hearing the news and reading the guy's writings, immediately identified with his victims. They've felt that weird stare from across the room, received abusive texts from people they rejected. They haven't said much in this thread (I wonder why?) but there are many of them out there.
If you find yourself reading through this guy's writings and feeling those uncomfortable moments of recognition, I suggest you stop for a moment and try to recognise yourself in the 'enemies' he talks about. Ever hung out in a coffee shop with a girl? You could have been a victim. Ever been black while being with a girl? He'd have hated your guts. Ever driven a Honda Civic with a girl in the passenger seat? etc. The girl needn't have been your girlfriend; your sister or co-worker might have been enough to earn you a spot on his list. He doesn't seem to have done much investigation before pronouncing judgement.
After doing what I suggest, if you still find yourself wanting to unload your inner pain on NeoGAF it might be time to seek assistance from a counsellor or medical professional. You won't get good help here but there are resources out there and there is no shame in accessing them.