...and it's called freedom of speech.
(to add on some explanation of it, wink wink @BuildASnowman)
By that, I don't mean you can say your opinion in whatever manner you want, you can only say your opinion respectfully.
Why it's related? Because I think there needs to be more respect for opinions. Flame wars (or as I call them "opinion wars") are simply caused by people disagreeing and trying to make their opinion "right". You may say it's those annoying people who disagree, but it's also the other person's fault for being in the fight and even bothering.
Also, opinions shouldn't influence behaviors even in trusted people because 1. it makes a bad influence 2. it can cause the person to abuse rights.
PLEASE DON'T FLAG OR CLOSE THIS TOPIC UNLESS SOMEONE SAYS SOMETHING LEGITIMATELY INAPPROPIATE