When people pretend to be nice they often are accused of being "fake" once they get "exposed". The question is whether it is more ethical to pretend to be nice yet risk being exposed as fake or be mean but real? Do people really care about the difference between fake and real more than how they are being treated?
What would you prefer? Someone who pretends to be nice to you but who really doesn't think very highly like you like how they are treating you? Or someone who treats you exactly how they think of you, at all times? Is being nice just having better etiquette?
I prefer people who act nice to me even if they don't like me personally if it is a professional or formal setting. In an informal setting if a person does not like me then I would rather they not stay around me because I don't want to be around people who have a problem with me.