The Backfire Effect is part of a larger physiological phenomenon called Confirmation Bias. Confirmation Bias is the human desire to seek information that backs up what we already believe and avoid information that disproves our beliefs. A Backfire occurs with more emotionally drawn positions, like politics or abortion, that causes us not only to disregard information that disproves our beliefs but actually see such information as an attack requiring is to further entrench our (wrong) position.
In simple terms the Backfire Effect is us doubling-down on a position we have solid evidence is wrong. In recent years the highest profile person that public acts on the Backfire Effect is President Trump. It is not that he is wrong in some of his positions it is that he is veritably wrong in some of his positions.
In fairness to President Trump anyone else involved in a public life, (government officials, actors, activists…) there is much research on the effects of “public commitment”. Once a person has stated their position publicly, it is much less likely they will change their position even after being presented with verifiable facts that contravene the position.
I am sure you can think of examples in your own life in which you have stated something, later found it to be untrue but had difficulty admitting it. We all like to be right. Now imagine stating your position to millions of people, later finding out it was wrong and having to adjust course so publicly. That is not easy and it takes someone with a strong constitution. Many of us are too weak to publicly admit our mistakes.
Social media companies study your actions (what you read, what you click ‘like’ on, what you retweet…) to create a profile about you. That profile is then used to feed you tweets and posts that fit with your world view. This is going to supercharge your Confirmation Bias. What you see is what you expect and little else. When the social media algorithms or a friend sends you tweets and posts presenting facts conflicting with your stated beliefs, it is easy to ignore them and in fact double down on your position by confirming it with the ‘facts’ the social media system is feeding you.
This is why you should not ‘get your news’ from Social Media like Facebook and Twitter. They are, by design, intended to keep you engaged by sending you things they know you already agree with. That MIGHT be facts and news, but is not likely to be propaganda.