The "Sir" Charade

When did the term "Sir" become a disparaging remark? I've noticed that over time, the term has become an increasingly easy way for someone to express their distaste or insult you while being as polite as possible. Some examples include, "Sir, it's your turn", or "Sir, you are holding up the line", or even "Can I help you, Sir?". The really irate subject will give you a "Sir" sandwich, as in "Sir, you're making a scene, Sir". This is modeled after the military, where a "Sir, yes, Sir" is the affirmative response, but I wouldn't take that as a sign of respect, the soldier is only speaking that way because he is terrified.

There are only three instances I can think of where you are pretty much ok, and that is the "Thank you (or You're welcome), Sir", the "I'm sorry, Sir", and the "Excuse me, Sir". But even those can be insulting if the intonation of speech is compromised. Even people who start a letter with "Dear Sir/Madam" might be only doing so because they figured your name wasn't important enough to figure out beforehand.

The word "Sir" was intended to refer to someone of superior rank or age, as in a Knight or some other type of nobleman. A way to express that the person speaking it was voluntarily subjugating themselves out of respect. Now, it's become a polite way of telling you to go fuck yourself.