I have little understanding of 'common' etiquette because I have always lived in unusual subcultures. So if you think I am being rude to you, it is extremely likely that it is an accident. UNLESS you're a privileged person talking about oppression - then I am most likely being rude on purpose.
People seem to think that my recent development of rudeness toward defaults is a product of emotion or perhaps burnout. It isn't. I'm very skilled at remaining calm in conflict, and very skilled at phrasing things delicately when I feel the need. And I'm good at disengaging from unproductive conversations without emotional difficulty. It is much easier to just not engage at all with defaults. It's emotionally easier to obey their rules of conduct and thus deny them their favorite argument, "if you had been nice I might have let your thoughts matter."
My choice to be rude is deliberate. I know that a person truly wanting to be kind and decent will learn no matter the tone, so I say things partly for the silent observers.
But mostly, I do this because defaults (white cis etc men) never get called on their bullshit. They think they're right and they think people like them because no one ever tells them otherwise. I can do this safely because of my relative privilege, and so I will. If more people demanded evidence for their baseless claims and mocked them for their lack of skills at empathy and critical analysis, they might eventually start realizing that something is wrong with them. I can promise you that arguing politely is never going to change their mind. Scorn, dislike, and dismissal might, since it's a new experience. So, when I tell a white man that their opinions on things they haven't experienced are useless, ridiculous, and unwanted, I feel quite strongly that I am making the world a better place.
I know a few decent defaults, maybe 6 total. I know it is possible for me to be rude and for them to know that I value them and consider them worthy people. All it takes to be decent is to accept other people's experiences as reality, understand that you cannot understand oppression you don't experience without being taught, humbly seek to learn without being defensive, and apply what you learn.
(Pripoi means privilege-poisoned.)