but words like nigger and cunt are generally used solely to hurt, which is one of the things we're not supposed to use words for. They can still be used, e.g., "John called Martin a 'nigger'", in which case it's perfectly fine - it's conveying factual information. Much different than the dude that actually used it against Martin.
Words like fuck and shit and damn are, in general, fine - rude in a social context, sure, but that's only because our society is immature, not because the words are ipso facto rude or vulgar - but nothing morally or ethically wrong with any of them, unless one is using them to hurt, i.e., "You're a stupid fuck" or "Someone oughtta shit in your mouth", which sentences would still be offensive even without the fuck or the shit in them.
Using these so-called "swear words" is, alas, socially inappropriate - they really shouldn't be, but people years ago decided that those words are "offensive", and now they can't be used in public. I find it unfortunate, because there are times that one of them is just the right word to punctuate a thought, e.g., compare "Please, hie yourself elsewhere" versus "Fuck off!", or "this works really well" versus "This works like a motherfucker".
Eph 4:29 says
"Let no evil talk come out of your mouths, but only what is useful for building up, as there is need, so that your words may give grace to those who hear."
Notice the "evil" in there.
Ehp 5:4 says
"Entirely out of place is obscene, silly, and vulgar talk; but instead, let there be thanksgiving."
Swear words are, in a lot of cases (except when used creatively) a lower class form of speech, and thus vulgar. But notice the proscription here is only that such language is "out of place", not morally reprehensible, and also compares it versus thanksgiving - and so one can assume that Paul is talking here mostly about language that is 'obscene, silly, and vulgar' is language which is not language of thanksgiving - petty complaints, gossip, name-calling, and so forth. Again, not a prohibition of "shit".
Col 3:8 says
"But now you must get rid of all such things--anger, wrath, malice, slander, and abusive language from your mouth."
None of those modifiers say anything about "swear" words. Those are all forms of words spoken with the intent to hurt.
I don't think there is any phonetic combination that is offensive to God in and of itself. Heck, the Thai people have a word "Phuket" - are they blasphmening God by using it? Of course not.
What offends God, as I see it, is how we USE language.
I find it unfortunate that we even have phonetic combinations that we deem "profane" (which is a truly ridiculous notion if one actually knows the meaning of profane) or "obscene". If we would collectively decide that they aren't, they would lose their power, and we go on with the act of living and stop worry about how other people are living.
The whole "swear word"/"bad word" bullshit is solely asshole rich people and overly-pious-but-really-hypocritical-fuckwit assholes finding yet another theological justification for despising the lower classes.