It's a very easy, very direct, not at all impolite way to express your desires in any situation.

这是个非常简单而直接的句型，用这样的句型在各种情形下表达你的愿望也不会显得不礼貌。

I want to 课堂 - SpeakingMax英语口语达人

It's a really disgusting habit and you have to stop doing this. It's so impolite.

这真是个令人作呕的习惯。你一定要改掉。这样太没礼貌了。

have to 实战 - SpeakingMax英语口语达人

It's considered impolite to hand a name card to someone using one hand.

ECONOMIST: Business travel

Kaufman was never impolite to me (more like a nod), but she certainly focused on the fellows.

FORBES: Elaine Kaufman Remembered As Hostess Of Big Boys Of New York

Also, not to be impolite or anything, but how expressive is a fish, until it hits a grill?

NEWYORKER: Finding Nemo