What I would describe as a chav is anybody who displays the following behaviour;
*Dressing in various identity concealing ways (hoods up with cap and scarf in perfectly mild conditions, possibly all black at night).
*spitting, swearing excessively and loudly at anyone and everyone, damaging public property
*only fight in gangs and only against someone who appears vulnerable
*intimidate random vulnerable people (younger people, old people).
Other characteristics too, they're the main ones. I know people who work who behave like this, its nothing to do with bashing vulnerable people. anyone who behaves like this - if he queen of england herself behaved like this - is what I would describe as a chav. That's what everyone I know describes a chav as. No thought is given to their employment or class status.
Its all well and good wanting to help vulnerable people, but you also need to accept that some people are just plain arseholes who enjoy acting like that, and don't deserve to have excuses made up for them so that they can continue their ridiculous antics.