I'm going to assert that a key component in being rude is being offensive. And I think that being offensive needs to be separated from someone being offended.

Here's what I mean. I've got some distant relatives who think I'm being rude because unlike them I don't get into an escalating argument with my wife over trivial things at family events that cumulates in a shouting match.

I'm absolutely breaking their social norms by having a positive relationship with my wife and they're definitely offended by it. However, to say that I'm being offensive or rude robs those words of their meaning.