Okay, emo is basically whiny hardcore punk. Not pop punk, not metal, hardcore punk. It's supposed to be emocore.
But people have taken to describing emo as anything whiny/depressing/sad. It's almost like you can label anything emo to sell it. I guess Guns n' Roses was emo too though, since Axl Rose is a whiny annoying *****. Nine Inch Nails is emo because Trent Reznor is always depressed and angry at the world. Johnny Cash is emo, not only because a lot of emo kids listen to him, but because he's always singing about some guy in jail who is about to die. Depeche Mode may actually qualify as emo. The Backstreet boys are emo because they are always singing about girls. Weezer is emo because Rivers wears thick rimmed glasses. Simple Plan is emo because they are pampered middle class kids. Nirvana was emo. If Massassi started a band, we would most certainly be emo, even if we played two tone ska.
http://en.wikipedia.org/wiki/Emo_%28music%29
Hot Water Music is emo. Simple Plan is not. I don't like either, but it's annoying when people call everything emo, because then it ends up being that I don't have any way to know wether or not I'm going to dislike a band because they have monotonous screaming and super repetetive lead lines.
However, if you are just talking about people, yeah, emo can be used to describe lots of people, like gbk >_>. But calling Simple Plan emo is just ignorant.
http://en.wikipedia.org/wiki/Emo_%28slang%29
Epstein didn't kill himself.