Not to disagree, there's interesting stuff in the nature of "posh" english and how it has shifted over time. I am told a lot of racing slang wound up being used by upper class twits, Polari was picked up by art college students. Everyone speaks a bit Essex now.
Scots has it's own posh and working class, as does Liverpool and Newcastle. Even in regions, you can tell. "sex is what morningside ladies get their coal in" and all.
The content of the article is a bit more nuanced than the headline.
The study was about perception of accents from different regions: Belfast, Birmingham, Bradford, Bristol, Cardiff, Glasgow, Liverpool, London, Newcastle and standard southern British English (also known as received pronunciation).
The participants were asked to rate the voices on 10 social traits: educated, intelligent, rich, working class, friendly, honest, kind, trustworthy, aggressive and confident; as well as on 10 morally good, bad and ambiguous behaviours that included a range of crime types.
The article doesn't say that the study showed that some participants rated some accents as being more working class than others. We have to assume that the study did find that, otherwise the article is complete nonsense.
So, we must conclude that "working class" correlated with "likelihood of committing certain crimes". Again, the article doesn't actually say that.
But still, RP (received pronunciation) is an upper-class accent, and it came in at 3rd place as "likely to commit a sexual assault".
Studies like this sometimes pop up absurd correlations though. See this xkcd: https://xkcd.com/882/
