"Chavs" was originally UK anti-Gypsy slang, much like "N*ggers" in the USA.
It has for roughly five years been used as a group name by middle class English youth to describe their working class (poorer) opposite numbers (usually white and applying to both sexes). It isn't a neutral term: it means ugly, smelly, dirty and so on.
The person using the term most likely considers themselves more sensitive, more artisitc, more open-minded, and more "against teh system!!1!" than the "chavs", and is simply not interested in the following ludicrous ideas:
a) working class people do not all pose a threat to one's health/expensive mobile phone/taxpayer's money(!!11!!)
b) working class people who do pose a threat may do so because of their treatment by the economic system, and not through their own personalities
c) hating working class people based on the fact they can't afford the same expensive "anti-establishment" (Hot Topic and similar) clothes as you is actually playing straight into the hands of the establishment
d) why is Pete Doherty cool but "OMG some smackhead on the street isn't"
e) the working class are "people"
Middle class young dude: "OMG LOL I saw this Chav woman before with two kids I was like OMG why don't I just kick those kids in the face with my converse trainers like Chuck Norris OMG I should kill them all like that Hitler dude that'd be cool ROFL she's not gonna steal my mobile when I totally kick her kids in the head lol"
His friend: "Yeah I know Chavs aren't very nice people when you think about it"