Can't be arsed to trawl through six pages of back and forth regarding L'emos (as they are known in the French Provinces) so will leave my tight brown coil of opinion on the lawn and scarper.
Emo can refer to several related groups that some feel they relate to or belong to.
Emo - self harming mild depressive: This group could do with a collective hug. Worried by social problems or stigma (potentially paranoid), they resort to reliable despair and cheap pain based biochemical thrills (as opposed to expensive powder based ones.)
Emo - nerdy kid showing interest in some facets of "alternative" culture: This group will grow out of it. They may have been influenced by friends (especially those in my final sub-genus of emo) or television or, sweet baby Jesus forbid, the internet. They cannot identify with the "Grade one all over" tracksuit wearing types nor with the idols that their parents or peers bow to (probably not the same idols) so they conform to a new standard set by Gerrard Way. They may feel shunned by other groups and this angst ties them to the first group.
Emo - perfectly styled fringe wearer, glasses optional - This one was the first. He/she is the progenitor of the trend. They saw something that didn't exist in their locality (i.e American Pop-punk coming out of Smethwick) and decided they would spread it. That way, they will be flavour of the month and, when it grows to encompass those they share no love for, they can cast it off as "something I did yeeeeeaaaaarrrrssss ago". They know nothing of emotions, they are just in fashion.
To conclude; I propose the hatred deserved by each group increases as they distance themselves from actually being depressed. Self-harmers do no harm to anyone but themselves. Nerdy emo kids are always going to be the target of abuse from some groups, whether they are nerdy gymnasts or nerdy stoners or nerdy "subcategory". Those who base their personal appearance on social trends and the opinions of others are simply shallow and, ultimately, gleaming purple pork swords.
OT: I fucking hate emos.