While it's true that some people have a tendency to paint anyone with an overt accent and a penchant for designer sportswear as a "chav", to me it has pretty much the same meaning as "yob" used to (ie: loud-mouthed, violent, disrespectful idiots). It didn't start off as a term of endearment, I know that much; and I doubt the people AF is referring to are simply innocent followers of fashion.
People are bound to question others' motivation to have children when they don't have the means to look after their children or actually seem to do any parenting. Perhaps the moderately more intelligent/educated people tend to think the less intelligent/educated are as capable of cunning and manipulation as they are. They need to find rational motivation for reproduction which to them looks to have none. But anyone who actually knows what's going on realises that the main reasons for having children are biological impulse and emotional fulfilment. People have kids no matter whether they can afford to look after them or not (look at Africa). They are certainly guilty of not examining the consequences of having children, but that's because they aren't intelligent/educated enough to understand the implications. They aren't able to take a step back and say "Actually, it's not a good idea for me to have children because I can't afford to look after them / I have no parenting skills / the world is overpopulated enough as it is". The thought simply doesn't cross their minds. They have children because it's a natural thing to do.