I recently came across this article:
Which uses (and therefore teaches) swear words.The English translations are censored, but the Spanish (the language being taught in the article) are not.
I thought it was an unwritten rule, that you don't teach adult language (+slang) to beginners/intermediates.
It made me think about my own rules for learning/teaching "bad" words.
I would never teach swear words to a beginner who is interested in becoming fluent in my language.
But if you are not interested in learning and actually communicating in the language and are only curious about having fun, then I can teach you some funny adult language (I'm talking about foreign friends in real life, not here on Italki).
As for learning...
I avoid bad words, after unknowingly swearing in German when I was in elementary school (After watching too many episodes of "Cobra 11" (German police drama) instead of saying "Leise" I said.......something else).
What is your opinion on the matter?
Yes, I think you are right. A beginner should ideally know formal, polite English*. That way they can communicate all around the English speaking world without much problems. After that they will be independent, and can choose to learn no more or colloquial English or slang or swear words, depending on their preference.
*or, any language.
If adults want to learn swear words, that's their business. Adult, is the key word here. Of course, no one is obliged to teach them if they don't want to. As long as you are paying, you are in charge.
I have always had a strong suspicion that people who rail against cuss words are users of them. They just don't want to admit it on a public forum.
I've seen research that says cussing is a healthy activity from a mental health standpoint. But I have #@$$% no idea if that's true.