The fact that something is generally considered (by whom? what does that mean? how do you know? what/who are you basing this statement on?) to be vulgar or obscene doesn't necessarily make it so. And in any case, you'd first have to prove the truth of the statement that some words are generally considered to be vulgar or obscene.
In addition, I suggest that if what you state is true, it is still not the words that are vulgar or obscene, but what they name or describe is considered vulgar or obscene. For example, take the word 'cunt'. Essentially, it is a name for female genitalia. There is nothing vulgar or obscene about a part of the female body. BUT, the word is sometimes used as a way of being unpleasant towards someone. It is used as an insult. Even when it is used as an insult, the word is not vulgar or obscene. It is the person's use of the word, and possibly the person using it who is vulgar because they are associating a normal part of the female human body with disgustingness. There's no reason to do that unless the user is having disgusting thoughts and wants to be nasty. It's the person who is nasty, not the word.
Once again, it is the meaning attached, and the connotations of the meaning, that are problematic. Or, to out it another way, it is the intention of the speaker of such words that is the problem, not the words.
An Ecuadorean friend of mine who sometimes worried that his English would be misunderstood used to say "Listen to the meaning of what I'm saying, not just the words." It's a good approach.