Here is a popular legend by Arthur Schopenhauer, “It is a wise thing to be polite; consequently, it is a stupid thing to be rude. To make enemies by unnecessary and willful incivility is just as insane a proceeding as to set your house on fire. For politeness is like a counter—an avowedly false coin, with which it is foolish to be stingy.”
Politeness/courtesy will cost a person nothing; it will only open several doors that everybody deem hard to open, take you places that rude persons won't get to and this will be done in record speed. In contrast, being rude or impolite will cost you a lot; it will cause all doors to be shut, enemies will be brewed in record speed and at the tick of the clock, finally a person’s downfall.
Choose courtesy and politeness over rudeness/incivility and see where it takes you.