One of the key things to remember with this concept is that this specifically in regards to acting. We have very good reasons for being polite in our normal everyday world. Politeness serves a social function. If it didn’t, we wouldn’t use it. It greases the wheels of social interaction and allows us to move forward without getting too involved in non-essential interactions.
So why is it such a bad thing for our acting? It is precisely for why it’s a “good” thing in civilized society! In acting, we don’t want to sidestep potentially negative (or intensely positive, for that matter) interactions with others! Those are exactly the kind of interactions we are seeking out! By holding onto the idea of being polite, considerate and even kind (when consideration and kindness come out of a sense of social obligation), we stop ourselves from really feeling deeply about the other person.
Politeness by definition gets in the way of us expressing how we truly feel. It takes us out of the moment, because every impulse, every response must be checked for the impact it might have on the other person. That takes a lot of attention away from what’s happening around us and puts it back on us. In acting, at the foundation, we want a free expression of how we feel. And that freedom comes from the complete lack of self-censorship.
But then you’re asking me to be rude! you might think. No. Being rude, in this context is not the opposite of being polite. Rudeness implies that you’re trying to have an effect on the other person: you’re trying to move them in some way. But in this exercise, we are neither trying to “help” the other person by keeping the truth from them, nor hurt them by attacking them or being mean to them. Our goal is simply to tell them the truth as we see it. Simply express to them how we feel about them, to let out our reactions to their behavior as fully as possible. It’s cliche, but we strive to do it the way a 2 year old would on the playground. Not out to get someone or try to make it easier on them. Just simply tell them the truth.