RE: Kidd O.
A particular genre title implies a particular general "feel" to music. If I claim my music is "progressive" that doesn't mean it's liberal and forward thinking. I mean, shit, I could argue (and argue convincingly) that punk and industrial are progressive. But the spirit of the title "progressive" is arena rock with complex technical music that is heavily influenced by classical and nonwestern music that often relies on both superior musicianship and esoteric chord progressions, time signatures, synchopation, etc. Thus, while Bad Religion may be politically progressive, King Crimson, which pretty much stays out of politics, is progressive rock.
If I say "music to dance to" that could mean ANY music. People used to dance to classical music. And jazz. And tribal music. And hell, you can even dance to punk. But the term "dance music" implies a particular spirit, and that spirit is not embodied by indie rock, prog rock, punk, post-hardcore, black metal, or any of a thousand other genres. It is embodied by electronica, and even then, only some electronica (and industrial) can really fit this bill. Thus, I could dance my ass off to Arcade Fire, but they are not dance music, and most people wouldn't dance to Frontline Assembly (I don't really know why, though) and that IS dance music.
Genres have a million different purposes and I'm not going to get into them all right now. While subgenres and smaller partitions (e.g. post-punk vs. post-hardcore) are highly debatable, major genres are pretty solid. Everyone knows what metal, electronica, hip-hop, punk, alt-rock, and so forth mean, even if they don't know the difference between, say, trance and house. Pulling a "who cares about genre names?" whine just because you don't want to admit that you were wrong is just lame. And overkill.