Unfortunately telling someone that someone else is wrong will only be any use if they are intelligent enough to look at both sides or have enough education to understand your point of view and that maybe your right and they should look deeper into the other claims.
Critical thinking is sorely lacking in the general population but you would think people in science, engineering, math would be well equipped in this regard and while probably better than the general population I still find cases which are difficult to understand or justify.
I am always amused by the "sovereign citizen" types who live in an alternative reality and no amount of evidence to the contrary will make them question their beliefs. You can see plenty of videos and reports of these guys being dragged to jail, tasered, fined, etc. You cannot find any reports of their loony theories prevailing and yet they insist they are right and the rest of the world is wrong. I am amazed at how some people can be so immune to obvious facts, to evidence. They have made up their own reality in their minds and anything that does not match that is just ignored. It takes a special level of pigheadedness to insist like that even after the cops taser you and then the judge throws you in jail. To keep saying "they can't do that" because I know some magical words ("joinder", etc.) that will stop them.
I have a friend here in Spain who has a daughter who is married in England and has lived and worked there for the better part of two decades. We get together for lunch every few months and we have exactly the same conversation over and over again. He says his daughter would like to take UK citizenship if it weren't because she would have to renounce her Spanish citizenship. Then I say that is not so and remind him I have sent him several times emails with links to UK government sites where they say you do not have to renounce another citizenship in order to acquire UK citizenship. In fact it is not easy to lose UK citizenship. He listens like it is the first time he hears it. Then, a few months later, we have the same conversation all over again.
Some people are just immune to facts and reason. They will assert X which makes no sense and when asked to provide evidence and support for their assertion they will disappear or just say "look it up". They know there is no evidence in support of their position but they will not reconsider.
I read an article about how people, when their beliefs are challenged with evidence and facts and shown to be wrong, most people will not reconsider and will come away with stronger support for that position they held. People get invested in a certain position and any challenge is taken as a challenge to them personally.
Again, we need to learn and teach to think critically and search for facts and truth. The scientific method.
Don Lancaster has a lot of common sense, not only in matters of science and technology but also in matters of general getting around life. I cited his
"Case Against Patents" as an example. Some people think you can just have a great idea, patent it and count the money as it rolls in. In practice it does not work like that.