I'm inclined to think that there are differences of opinion about this, but my own view (for what it is worth) is that what counts as vulgar and obscene are a matter of cultural (and perhaps even situational) context. For one thing, the origin of the word "vulgar" simply associates a thing with the masses, or the common people--so identifying a term as "vulgar" really only associates that term with a certain social class. Only if we think of that class as a whole as somehow morally debased would vulgarity (in this sense) count as a kind of evil. But I understand that "vulgar" has lost its "classist" bias and now means something like "dirty" or "obscene." At any rate, the word "fuck" doesn't seem to me to have some intrinsic feature that makes it obscene. What it does have is a kind of resonance or set of connotations, which are culture-bound, that make its uses rude in "polite company." Now, some might object to the connections between the word "fuck" and the sex act to which it...

Most historians of philosophy agree that definitional questions were introduced as the special province of philosophy by Socrates, who asked them about virtue-terms, and thus invariably exposed the ignorance of his interlocutors. Socrates is also sometimes said to have committed "the Socratic fallacy," which is (roughly) the claim that unless you have knowledge of the definition, you can't know anything else about the thing to be defined, including that any instance of it really is an instance. Some very prominent scholars continue to think that Socrates believed in this kind of epistemological priority of definition, which your car example shows well would be a fallacy (if indeed Socrates held such a view, though I have argued in my published work that he did not). Anyway, of course you can know that a certain Chevy Impala is a car, even if you don't know how to define "car." So definitional knowledge is plainly not epistemologically prior to our ability to know instances. I am not...

I hope others will add to what I have to say here. But it seems to me that the actual question you ask here is really more one for social science than for philosophy--in other words, the answer to your questions, as framed, strike me as likely to come from empirical study (which is not the main province of philosophy). My own hypothesis, for what it is worth (probably little!) is that the way we speak very much DOES influence the way we act. If I am right about this, then a legitimate philosophical question would be: How should we speak?