Really? In that case, let's just screen all art right now. No more art allowed. Let's see how the world turns out now that we can't draw. I'm not trying to hate on those people, and I respect their beliefs, but they won't be looking for art, because it's offensive to them.
About strong language. The FAQ that you quite correctly quoted says ".Can be applied to deviations containing profanity, vulgarity, and otherwise coarse or offensive language at the discretion of the submitter". Note the word can. There is no rule on dA saying that strong language has to be marked as having Mature Content.
That's not the point. The point is that people are harmed by hearing these words. They are inappropriate, rude, insensitive, uncultured, and usually refer to sexual things. This is why it's a problem. (I have other reasons, but they are usually not listened to/blatantly ignored/etc)
They're not harmed simply by seeing or hearing words. If someone uses abusive language towards you, then fair enough, that's upsetting. But it's entirely possible to be abusive towards someone without ever swearing at them - it's about context and behaviour. Simply seeing the word fuck, for example, doesn't do anyone any harm at all.
Part of the problem, however, is that people swear too much. The vocabulary of the average person has shrunk, and rather than actually elaborating on a statement, one generally swears to prove a point. I see this all the time. Abusive language towards a person is generally wrong, but the reason these words are bad is because they are used so much. I am perfectly fine with swearing at an appropriate occasion. For example, in Harry Potter, book seven, when Mrs. Weasley destroys Bellatrix, what else can you call her? Context and behavior do have an effect, but what's the point of swearing, then? Is it just to prove how cool you are? Because it's just showing how your vocabulary is less than average. (Though, at this point, that probably is average.) It's not funny, or cute, or cool. It's just stupid. And actually, seeing swear words does hurt me. It makes me want to curl up in a corner and hide from the death of humanity. Yes, that is a bit hyperbolic, but it's kind of what I feel. Also, that last sentance is funny, because I have a word replacer in chrome. I keep forgetting I have it and that other people don't actually say things like "crudmuffin" and "derpface" very often.
[link] Swearing doesn't mean someones' vocabulary is less than average. Just because people around you (teens or whatever their 'status' is) or those you expect to be of different swears doesn't mean they are less than average in vocabulary. They choose not to do that. Apologies if someone doesn't use 'preposterous' instead of bullshit or rubbish. o_O And many who you think have higher vocabularies can and do swear. Your personal opinions on this does not show actual basis for that. Some also feel saying "no" is absolutely offensive here when someone disagrees. And thinking that way would not develop anything better but just block expression. If someone is harassing you as such through use of abusive language/swear words, block and report if it continues. One can be 'abusive' without using swear words.