politeness and rudeness seem like the same domain approached from opposite sides. If somebody asks "is doing X considered polite in (context)?" he'll probably tag it "politeness", but if he asks "would it be rude to X in (context)?" he'll probably tag it "rudeness". A future visitor using tags has a 50-50 chance of seeing the question.
Do we need both?
The wiki for politeness:
A behaviour that is respectful and considerate of other people. To be used when consideration, tact, deference, or courtesy is on the line.
This tag can be used for questions about a behaviour that is respectful and considerate of other people. Since it is a culturally defined phenomenon, therefore what is considered polite in one culture can sometimes be quite rude or simply eccentric in another cultural context. So, a cultural tag such as united-states or united-kingdom should be used with this.
The wiki for rudeness:
For questions where rudeness is pertinent to any party of an encounter. The questioners own rudeness or the questioner being subject to someone else's rudeness or the questioner observing someone being rude to a third party.
There are some people in life that can come across as rude, or can overtly try to be rude to the people around them. Often in these situations it can be difficult to interact with them, reason with them, or just in general be with them. In addition some people can come across as rude without even meaning to when trying to achieve a certain goal or reply to a certain comment in a certain way. Questions here are about how to deal with rude people, but also situations where people come across as rude, and even situations where you may appear to be rude, even when that was not the intention.
This tag should be used with tags such as friends and united-kingdom.
Neither wiki references the other. If we keep both tags, we should probably cross-reference them.