Etiquette: You are not exempt from it.

I suspect I am not the only person this has happened to. Tell me when this starts sounding familiar: You spend the first decade or so under the careful tutelage of your parents, who do their absolute damnedest to instill good manners and etiquette in you, their offspring. If your upbringing was similar to mine, this also involved being taken to various formal events where it was an unspoken fact that bad behavior would be eliminated with extreme prejudice, further cementing the behavior. You may not think of yourself as egregiously polite or well mannered, but that’s primarily because you spend most of your time in contact with those who hold themselves to a similar standard, whether any of you know it or not. Everything is dandy.
Then one day you find yourself in an environment where none of this holds true. This may or may not occur when one is in any level of grade school. For myself, I certainly experienced less than pleasant exchanges with many of my fellow students in high school, but I usually chalked that up to their dislike of me, rather than their having been raised in a barn. My big awakening occurred at Miskatonic. ANYWAY, you have been dropped on your ass amongst a bunch of cretins who don’t say please, thank you, or bother with utensils. Usually, I find, this inspires rage and frustration in the subject, and, if you’re Hannibal Lecter, psychopathic behavior. For me, it certainly entrenched my misanthropic view of humanity even deeper.

So let’s get something straight here: MANNERS ARE NOT OPTIONAL, FOR ANYONE. They provide orchestration and direction that prevents idiotic mishaps. Perfect example: Last week I was going down a narrow, crowded stair case. I kept to the right, AS YOU SHOULD, and so did most people. A few jackasses, however, decided that the line wasn’t moving fast enough, went into the ‘oncoming’ lane, and tried to make a break for it…only to have people need to get past them on their way up. Cue massive pile-up and delay. And for those who say that manners are sexist, I have this reply: They shouldn’t be. Just as an example, everyone should hold doors for everyone else, gender being utterly besides the point, and those having doors held for them should thank the holder. (As a side note, I find most women to be far ruder than men. They don’t bother to hold doors, smack people with their purses, and act infuriatingly entitled in every damn way you can imagine. NOT ACCEPTABLE, FELLOW FEMALES.)
Finally, there comes a point where things just go to far and, in my opinion, the only correct response to such blatant rudeness is to throw it back in the face of its progenitor. To illustrate: The Miskatonic café has limited seating. Around lunch time, when I am usually there, the seating becomes even more limited when scores of troglodytes troupe in, drop their bags and coats on every table in sight, and then go to lunch, leaving their things, supposedly secure in the knowledge that the table in question is ‘saved’ for them and rendering people like me, who can’t get there till class lets out, SOL if they want to sit down to eat a meal like a civilized human being. After a few weeks of this, I lost my temper and decided to play their game. So if there is nowhere to sit in the café I MAKE a place, shoving people’s stuff to the side or transferring them to another table and taking what wasn’t theirs to begin with. Obviously I’ve received blowback for doing so, but in every case I’ve been able to use a combination of good manners and a pointedly worded explanation that should make the idiot brigade in question think twice before usurping a table they won’t even be using. 
As an added bonus, manners are far more productive than *eating* someone, fava beans or no.