Woah..
Okay, first off I'm not 100% sure on what you want to say. You want people to stop calling emo music emo because all music is emotional?
Kay.. First, "emo" is call "emo" because, like you said, came from Emotional Hardcore, which (to my knowledge) came as an offshoot from Hardcore music in the 80s. It took a more melodic, rhythmic and deeper emotional approach, as opposed to hardcore's straight ahead angry thing.
When you said that The Clash and those other bands were angsty before "emo" existed you are right, but you wouldn't call those bands Emo. Because the term "Emo" came to describe a certain style of music that came from DC in the 80's.
Emo is a cultural term, just like pretty much every other genre name I can think of off the top of my head. Nowadays Indie music has a certain lyrical, musical and style characteristic about it, it doesn't just mean a band is on an indie label, in fact there are some Indie bands that are on Majors.
Okay, I think I'm getting away from your original point.
Most people have a general lack of understanding when it comes to music sub-genres, therefore, when they call something Emo, chances are they don't know what they are talking about.
Lets just leave it at that