I mean my first thought would be "show, don't tell". If you've got an intelligent idea, then you can go through all the steps that affluent people have gone through to verify it. You probably don't have the ability to conduct your own research, of course, but you can find the research of others and you can poke holes in the research of people you disagree with.
However, that might only work with people who were evaluating things based on the actual content of the research to begin with. If they aren't, you might have to Socratic method them a bit, ask them what they think makes 90% of scientists so special. You might also have to dig into the emotional motivations for their stubbornness.. Many people have invested a good bit of their identities into the way they think and believe, and so would need to develop a circle of friends that don't connect to such ideas or that are more intellectually open in order to feel safe changing their ideas. Some people have their own emotional experiences that have fixed their beliefs on a topic (the families of black people killed by police aren't going to be easy to convince that cops aren't racist, for instance), so in their case you may want to expose them to new and different horrific shit to literally blast their minds open--going back to the parenthetical about families, maybe show some graphic footage of blacks being killed by other blacks, or take them through the real life and decisions of a police officer with a video documentary or by getting them and a police officer to become friends or something. Shit like that.
Basically, understand why they think the way they do, and meet them there. Is my guess.