At the end of the day, human's are animals. We might think we're highly evolved and all that, but deep down we're animals and we have animal instincts. Just like other animals pick on/bully/attack/kill the smallest, or weakest or the members of their pack that stand out, humans do the same thing.
It's disgusting but until people change their mentality completely and become much more tolerant (which will never happen in any of our lifetimes, if at all), it's a sad fact that actions like this will happen all over the world.. and not just to the 'emos' but to any subculture that's seen as a threat, or seen simply as weak and needing to be stamped out- it's Darwin's theory, it's survival of the fittest, and human's can't seem to kick the habit, and realise, if they see themselves as evolved and superior and not simply animals, then they need to stop behaving like animals, and let people be.