Initially developed out of spite due to the likely verbal and physical attacks from 'chavs' or inebriated followers of mainstream activity, the term now seems to be applied with a sense of pride, to the extent of labelling and in some cases returning the verbal and physical abuse to the supposed 'trendy'.
The obvious irony in this statement is that, as is aforementioned, a select niche of society (namely, the alternative society)use this phrase almost exclusively (at least in this context) and yet they use it to somehow proclaim their individuality.
The truth, it would seem, is that it is an excuse. A way of excusing the fact that the populous don't like the way you look and the way you dress. They have their own reasons i'm sure, some well-founded, some slightly bigotted but still individual reasons that aren't incited by the media (no 'freak-bashing' music videos on MTV for example, or articles about how wrong dyeing your hair blue in the National Press). Due to this seemingly unanimous disapproval, this term is used to imply that the offending party doesn't like them because they are a trendy, and the accusing party is so out-there and hip and open-minded that the spoon-fed, publicised masses simply couldn't understand.
An element of denial is involed as well, the subculture referred to earlier has been ...