Why are you rude?

[Angrboda]

How can you love us? You're "new."

Also, I'm rude because I don't like an awful lot of people, and it's too much effort to be nice to them.

IMO, this is an honest and reasonable statement.  From my vantage point, it is somewhat irritating when someone, who I know does not like me (for whatever reason), is being "nice" to me.  This fake niceness is pretty apparent and comes off as insulting; I'd prefer people to make their honest feelings known rather than hide them behind a veil of fake feelings/behavior. 

That said, rather than pretend to be "nice" to people who I don't care too much for, especially if it is in the workplace where many work relationships are interdependent and avoidance would likely cause additional problems, I prefer to interact with them in a manner that is respectful and civil with the goal of  co-existing with them as realistically/painlessly as possible while hopefully minimizing any behavior on my part that could contribute to a negative conflict cycle. Obviously, this is a work in progress, but hopefully, as time progresses, I will become more skilled at it.  Thanks again for your post.