Swami Nikhilaananda said:
"Words for the biased mind, is like straightening the curved tail of a dog... A waste of time till you cut it off to end the ordeal"
A great quote to be remembered for all eternity. Have you ever given advice to a person who refuses to even let you speak? Have you ever argued with a person who does not even listen to you, or even if he/she does, refuses to accept it as true - or even consider it true for a moment, with the sole viewpoint that they are right and that the probability of you being right even remotely, is simply zilch... Instead, they keep talking about their points, and don't pay attention to you.
I have seen many such people, people with just mouths and no ears - they just speak, and seldom, mostly never, listen. I happened to speak to a friend of mine recently, and arose a topic where we had a difference of opinion. I was trying to explain my viewpoint to him. Unfortunately he had an opinion already formed, a pre-formed notion, and did not even listen to me - Instead, he just snubbed me, saying what I was speaking was incorrect. It was later proved that I was right afterall, but that's a whole different story.
When an opinion is already formed, rarely can a person suppress it for sometime, and look at the whole situation from an entirely different angle or viewpoint - meaning, most people have biased notions. This also introduces us to "out of the box" thinking. Why has "out of the box" thinking gained so much importance lately? Everyone is nowadays trained to think in a particular way. And once the training is complete, your thinking will be tuned to particular way only. Given a problem, your approach to it will be based on a pre-defined protocol. You won't be able to see the same problem from a different angle.
This becomes tiresome and frustrating in an argument... One usually tends to give up explaining, ending sentences with - "Do what you want..." When discussing, all view points and opinions need to be considered, correctly weighed, taking all consequences into account, pros and cons, and should come to an unbiased clear result. Never advice a person who's a mouth, not a ear.