What outcome would you rather have from a discussion? Learning the truth, or having your beliefs validated?
In a quiz competition, or while solving a math problem, those two things coincide. There is little room for doubt. However, in the real world, things can get more complicated. The truth may lie on a spectrum, whereas only one shade of light might be visible to us.
It is useful to go into discussions with the correct intention. What are you looking for? Learning or validation?
Now consider this question: what would you rather prefer, an honest and blunt answer or a polite answer?
Given this choice, most people pick the honest answer. It probably helps to ask ourselves this question before stepping into a discussion or a debate. By doing so, we set ourselves up for listening to hard truths.