I think jokes/joking comments are a different thing altogether, though. For me, funny is funny, and if you succeed in making me laugh, then I won't care if it was insensitive or what have you. I'd have laughed pretty hard at the above comment, and I'd have also known that you weren't being oblivious and rude, just trying to lighten the situation by injecting some humor.
That's the thing tho, isn't it? What's funny to an NT is perhaps offensive to someone else. We are quite hard to offend. Sometimes, even if I do find something hurtful/offensive, I'll reason myself out of it. I'll conclude that I've no right to feel that way. But most people won't. They always believe their feelings are entirely valid.
It seems to me that "rudeness" is a pretty subjective thing. The things I find rude (e.g. asking too many personal questions, invading my personal space, expecting me to participate in meaningless social rituals, judging my lifestyle, asking stupid questions rather than doing a bit of research) might be considered normal or inoffensive by the prevailing majority so I just have to put up with it.
The things I do that others might consider rude (stuff like being late, forgetting appointments and anniversaries, zoning out, forgetting to return a phone call, sarcastic humour, honest criticism, not smiling or engaging in mundane pleasantries) either don't bother me, or actually appeal when I encounter them in others. Why
should I embrace someone else's values about what is acceptable and what isn't?
I think truly rude people are either a) totally oblivious to the tone of their comments, b) not caring whether they come across as rude, because they're more concerned with themselves than others' feelings, or c) wanting to disarm/assert a dominant position through shock value or an attempt to lower someone's confidence or self-esteem.
Probably most NT fall in the a) category, because we have very little interest in being the alpha dog.
I don't think we're oblivious to the tone so much as oblivious as to the effect. In order to be aware of that effect you have to be able to empathise. But if what you are saying wouldn't cause you offense if someone said it to you, then empathy doesn't really work. Instead you have to learn a whole set of rules about how other people's minds work. It's like being mildly autistic.
Sometimes frustration and impatience emerge as rudeness/intolerance. We are known for not suffering fools gladly.
(c) is interesting. I hadn't thought of it as being a strategy for dominance. I like to shock (and be shocked, within reason) because I like novelty and hate cliche. Shock tactics can make you think about something in a new way, and I always welcome that. A lot of people don't though.