Quick definition for those who don't know: Cognitive dissonance occurs when a person's behavior and beliefs do not complement each other or when they hold two contradictory beliefs.
Story time! Please read this in it's entirety as there is important context as well as an actual point.
I have been spending some time with the in-laws over the past couple of weeks, because reasons. They are an immigrant family, but have been in the US since the tail end of the Vietnam war. All hold US citizenship and it's a large family.
Politics has cone up occasionally, but for the most part, we tend to steer away from those discussions when we mistakenly bring them up in conversation. Strangely enough, some are actually Trump supporters but I wouldn't go so far as to say anyone is full-blown "MAGA" or anything. I would describe the support as mild and truly ignorant of broader level politics.
So, there was some discussion about how immigrants needed to be kicked out of the US and there was support for mass deportations. Another conversation was about how "everyone"abused food stamps and welfare, but within about 10 mins, the discussion flipped to what products another person in the family could buy with their EBT card. Medicare and Medicaid is also a waste of the countries money, but then later there was a discussion about how to use those benefits for another family member.
Politics aside, cognitive dissonance is a bitch to deal with, especially when it's coupled with anecdotal evidence that may not even be real. I suspect that any experience with other "immigrants" I heard over the last couple of weeks are likely the result of a single, heavily biased experience coupled with gossip. (The gossip may create false memories of a situation the person believes is true. I think there is a special name for that.)
Telling a person bluntly that they are wrong is usually counter productive. Calling out the contradictions in beliefs can also be strangely unproductive as well. When a valid argument is made and a person realizes they can't resolve a conflicting belief, the tendency seems to be to fall back on a generic phrase like, "Well, I don't fully understand it, but that person must know what they are doing.", or something similar.
Provided that you actually give a shit, how do you go about cracking the shell of someone that has fallen victim to this kind of thing?
The best way, IME, is to know exactly in which ways these people are mistaken so you can ask the right questions until they're eventually left with untenable conclusions/information that doesn't fit reality. And it definitely helps if you state at all times that you're worried about the person, that you're not doing this because someone's paying you or for the fun of it but out of concern, that you could be chilling or doing anything else but you're here hoping you can get through to them, etc etc. But even then, at any moment they can just have a small 'frustration aneurysm' and leave the path of logic behind... In the end, we can't 'force' people to believe in what we believe in, regardless of how much sense it makes and/or how useful it would be for them; either we're open and clear minded enough to be reasonable or we're not. 🤷
When confronted with any questions that make people evaluate their dissonance people will often fall back on "I don't know" and refuse to engage information that contradicts their beliefs. If they do engage at all it may come in the form of circular logic, "Things are this way because they just are".
It can basically become a parent getting exasperated trying to explain why the sky is blue to a kid when they don't really know themselves.
The disconnect is often that their worldview is they are "right" and they just know that they are, and trying to prove otherwise kinda circles back on the sky argument. Saying that they are wrong is like telling them the sky is neon yellow, they know you're wrong in their mind.
So yeah I'm not sure how to get through to that other than people being social and usually abandoning ideas if they conflict with everyone around them and offer no options for people to engage with them, but that can be undone fast with an echo chamber of false information or really anything that reinforces their beliefs.