i have lived in neighborhoods below the poverty line, and i agree that swearing can be a sign of low emotional IQ. feeling is suppressed in poverty neighborhoods, expressing yourself with intelligence and emotional intelligence is dangerous. some people in these neighborhoods have emotional IQ, but it is so repressed that it has no outlet, so they turn to swearing to express emotions.
some, however, escape poverty by the strength of their will and do not want to forget it. we express our emotional IQ, but hold on to swearing and other remnants of our upbringing as part of our identity. it is difficult for some people to understand why someone who escaped these environments would hold on to pieces of them. but those are important parts of us, even if we rejected that life.
i suppose it depends on a person's definition of 'the working class'. i am proud to call myself a member of the working class. i do not want to "get out of it". the poverty neighborhoods i described in the rest of this post are an environment i do not want to return to, but they are a subset of the working class and not indicative of the entire class.