Someone being friendly to you is: Looking out for your interests.
Someone being polite to you is: Obeying social decorum.
People are very often highly polite and highly unfriendly at the same time.
The opposite way is greatly enjoyable and profitable.
That's true to a degree. Rules and laws don't dictate social custom, but they do strongly influence how it evolves over time. Note that it is very much possible to be polite (obey the rules of social decorum) and hostile (act aggressively against somebodies interests) simultaneously. The classic 'polite but strongly worded letter' from a lawyer (or publishing house) being the obvious example.
Tricky. Set the new rules and that's the new polite. Polite is whatever custom a group of people use to be understood and enjoy life together.
You poet, always leaving unfinished sentences and being mysterious, leaving to us the ingos (from the english word "integrate" and the greek word "logos", meaning: filling the blank between what is expressed and what is meant). It's good to know. I'll be more impolite from now on. You can now reference to this comment to know the origin of the word.
What a strong negative connotation! Judging. Judging things, judging people, being judgmental... these are not pleasant things that polite and civilized people do... right?
But if judging is such a fault, perhaps we should learn what exactly it is. Hmm... I don't know exactly. Maybe Merriam-Webster can enlighten us:
Judge. Transititive verb. "to form an opinion about through careful weighing of evidence and testing of premises"
Hmm. That's... not what we expected, now is it? Judging is bad. But forming an opinion through careful weighing of evidence and testing premises... that doesn't sound so bad. Hmm.
What does that sound like to me?
I'm nice. I'm socially 'nice'.
So in the society we live in, there are loads of little things, little lies that are viewed as being 'nice'. Lets start with really simple things - being polite. 'Could you please...?' 'Thank you' 'Would you mind if...?' Everyone should be polite to everyone else, whether or not you respect them its like the social interaction 0 state. You're polite to the people you tolerate, nasty to the people you hate and sweet to the people you like. Well, mostly.
And there's different ranges of politeness, for example, you're expected to be more polite to people who are older than you or of a higher status than you. Though I wouldn't say I agree with being polite to older people just cuz they're older, I do agree with being more polite - more respectful to the people of higher 'status' than you. Be that teachers, leaders, the glorious person who brings you your food at restaurants :p
Next point is about conversation. Most of the people that I interact on a daily basis talk about a certain range of things. So the guys I talk with mostly talk with me about girls/working out/music and the girls I talk to mostly talk with me about school/home/music/anime+manga. But then there are those few people that I talk to about shit I honestly don't give a fuck about: clothes/boys/youtubers
So if it doesn't interest me, why do I still talk with them about it? Well cuz I'm 'nice'. Its expected of you to show interest in the daily/personal life of the person you are conversing with: 'How was your day?' 'Do you like~~?' yep, you know what I mean. Small talk. Or more so, they get all into it: 'OMG he's so cute!! He talked to me today omg omg omg!!! and you're just there like: Mhm that's great...