I've gathered that people cut for the same reason others get drunk, or smoke pot. They want to take their minds off the other stresses in their lives for a little bit, physical pain replaces the emotional pain, then eventually it becomes habitual. To claim it's exclusive to kids who blindly follow a falsely labeled music genre is just plain silly.
Me? I just shrug my shoulders at threads like this and say "what the ****". They're kids, and we've all been there, following a trend thanks in part to a band. That's pop culture. We've also had bad days, ran away from home, or thought we were unloved and took it out on ourselves somehow. That's just how it goes. Granted, cutting is some mutation of self-pity, and how it evolved, I'll never know, but it is a mental illness, indeed.
Anyway, I think anyone who's ever participated in these threads has gotten a crash course in Emo 101 from AC. Just listen to what he's said and move on. Don't get bent out of shape because you find him abrasive. I'd be the same way if my explanations were neglected time and time again. It's as simple as this. "Emo" is just another bastardized fad that kids follow. It's misconstrued, misused, and for the misguided.
Thankfully, being the musical elitist that I am, with a roster of maybe 10-15 bands I listen to on a regular basis, and totally disgusted with today's metal scene, I don't have this problem. My interactivity with the meatheaded metal community is nil. I like what I like. I can be bopping to Full Blown Chaos in my car, wearing American Eagle clothes and not give a shit what anyone thinks of me.
I'm me. I'm out for me. I listen to what I like and dress how I tell myself to. How many other people can say that for themselves?