There must be a desire on both sides to get to the truth. If one of the sides already believes he knows what is truth, then its pointless. It becomes a situation where that person’s objective is not to get to the bottom of things, but to convince you he/she is right. Unconsciously I do this sometimes with some of my beliefs, and its hard not to do it. It requires some level of maturity, not getting attached to beliefs, and rather adhere to an uncertainty principle.
Another situation is acting in bad faith. Someone who gives zero shits about truth and its only desire is to advance his position/power.
The 1st example it might still be possible to bring the other around by hard facts, sometimes. The 2nd its hopeless because there is no desire for truth.
Sir, this is Lemmy.