If people won't listen to you, and keep telling you that you're wrong... maybe there's a point where you should start listening?
Being kind is important. Being right may or may not be important, depending on the situation.
If you have a medical emergency, I think it's much more important for me to be right if I'm telling you what to do than it is for me to be kind.
If you are working with me on a project, and you're making statements and decisions, you better be right. We're trying to build something, and don't want to screw up. I'm going to trust you if you act like you know something. If you are unsure, say that you're unsure. We can still be kind and polite to each other while doing that.
If you just broke up with your partner, and are upset. Being kind is more important, and I should be there to listen to you - it doesn't matter if you're right or not. It doesn't matter if I'm right or not.
Gosh! Situation and context matters. Imagine that! :)