The fact that something is a rule of etiquette is not adequate justification for being bound to that rule. That's considered rule warship.
That's why you're STILL missing the point. No one is
bound by anything because it's a matter of ETIQUETTE, not ethics. Etiquette IS relative. Proper etiquette varies by region and culture. Again, when in Rome, do as the Romans do. Etiquette doesn't need to be grounded in anything because no one (except you, because you're so hung up on it) is arguing for the universal truth or rightness of rules of etiquette. I'm speaking in relation to our society only. Etiquette can be as trivial as using the correct spoons for soup and salad at a formal dinner. There is no solid foundation in ethics for that rule, but it is etiquette nonetheless. You don't have to agree with the rules, you don't have to like the rules, and the rules don't even have to make sense to you. All that matters is that when you break the rules, people get pissed off. The rules themselves are not an ethical code and are not ethically founded, but they exist.
Now let me really spell this out for your intro level ass in regard to the example being discussed.
The fact that wearing a shirt with "TWAT" on it in public is poor etiquette in our society has already been established.
The jackass's failure to follow the etiquette rules in this case led to 97's mother being offended and put off, which is to be expected because that's exactly what the etiquette rules are designed to prevent.
It follows pretty simply (when you get above phil101) that biker douchebag failed in his duty to respect persons by offending an innocent lady with his failure to follow soceity's code of etiquette.
We have three issues here now. You aren't understanding because you're lumping them into one.
Issue #1: Biker wearing a shirt that says TWAT.
This issues DOES NOT break any rules of ethics.
This issues DOES NOT break any rules of etiquette.
Issue #2: Biker wearing a shirt that says TWAT in public.
This issue DOES NOT break any rules of ethics.
This issue
DOES break the rules of etiquette.
Issues #3: Biker's actions offend and inconvience 97's mother, thus failing to properly respect her.
This
DOES break the rules of ethics.
This issue
DOES break the rules of etiquette.
Are you understanding it now that it's broken down elementary style?
The last time I checked, Kant said good is created when people do what they ought to do, rather than what they want to do. He was also all about respect for persons and the inherent good in actions.
Although there is nothing inherently, ethically wrong with the word TWAT, and the biker is bound by no ethical rule that says he cannot wear the shirt in public, he OUGHT to have some repect for the people that are sensitive to the rules of etiquette. He has a duty to respect his fellow man, and that includes not having a "if they don't like it, fuck 'em" attitude.
You're biggest problem is that you cannot get over the idea that the nature of the word TWAT and rules of etiquette are not universal constants. You can't seem to grasp that I'm not trying to make a case for the universal rightness of our society's rules of etiquette. Honestly, I couldn't give two shits whether our rules of etiquette are ethically founded and universally applicable, because that not what I'm arguing. I'm arguing them in the context of only our own society, only in this particular case, and in the way in which they effect people. Once you get past the mind fuck that comes with the intro class and the feeling of knowing it all, and you come back to normal people land you'll be able to think clearly, less arrogantly, and less abstractly.