It is people that put their hearts into the work that made great things. Being polite should a technique rather than principal; if deeply in one's heart it is to make a great product. Also, when it's appropriate why not be rude to make things moving? Isn't it like the relationship of summer sunshine and winter snow; people perceive things based on different perspectives, as long as it's a natural reaction, why should we bother. I'd rather take candor rudeness than seemingly polite pretending. But of course, vice versa.