In case anyone’s wondering, ‘chav’ was a term that was over-popular in the British Isles about 16 to 8 years ago. It could be a term of abuse for a young working-class or poor person, or a name one might wear with honour, or even a style of dress which (at its finest) could be viewed as a descendant of ‘mod’ or ‘skinhead’.
People not from the UK exaggerate the class division enormously. In every country there are people who are suspicious of outsiders. Estates like the ones the boy and the girl in the video come from have similar problems to the ‘isolated farming communities’ where the USA’s Rednecks live. Fortunately, and unlike said farming communities, people from these estates are usually close to towns where they can interact with people from outside their community on a daily basis.
Still, I’ll admit concessions have to be made. Although I am not ‘posh’, my natural dialect is Received Pronunciation due to being brought up by teachers. I have been speaking bad English as an affectation ever since I was 12 just so that people don’t look at each other and say “eeeeooh, look at the little toff”.