Agreed for all parts except 11. It is a game, no need to troll your enemies. Don't necassarily need to comfort them either, but in a friendly game I think that is going a bit far. Though once it happens, there is nothing wrong with feeling good about the enemy team tearing themselves apart. Now, if it was tournament/ranked play or something serious, then I suppose it would be okay. Just as a matter of civility, winning is very important, but not that important.
EDIT: I should probably upload a game I played that demonstrates what you were saying very well. I was playing as morgana. Udyr was mad because Sion was accusing him of KS (which to a certain extent was the case, but not like Sion was making it out to be). Losing made this into a spiral. I don't remember what I said, but I got them to calm down, and we started winning. Then we lost because of a terrible judgement call on taking Baron at a bad time. But we did get very close to winning. As you can imagine, the game taking a 360 degree turn caused the enemy to start pointing fingers at each other as well. If it weren't for our bad Baron decision, we likely would have won. I think I was carrying =D.
EDIT2: Okay, I definately agree with taking advantage of the pompous ones LoL. Catch is, you don't even have to do much =D. Let them believe they can solo a teamfight, then watch them fail . Also, I would point out that negativity can be reduced by turning a player's "You're a noob" into "I'm awesome." Often, they don't really care which (or at least that is my experience), and so long as they don't run alone into a teamfight or something, it is at least tolerable. Oh wait, you said that =P.