Like many I have been dumbfounded by the willingness of people I used to think were perfectional who are willing to accept something I know to inaccurate and potentially dangerous. In many such cases, I believe I can offer facts and show that such facts are not just what I believe, but what experts and scientists also argue. Nothing. I try to assume that if I can get them to explain what they see as evidence for their position and often can get them to generate nothing in return. However, calling attention to this lack of support does not seem to matter. Push too hard or offer too much in reasons and evidence and it seems easy to generate an emotional backlash. I am completely mystified and concerned because an agreement on certain truths and facts seems absolutely necessary before serious matters can be addressed.
I found a reasonable analysis of this situation and my perceptions are not unique. I did not find the recommendations particularly useful. For example, the suggestion that one attempt to discuss a controversy out of the public eye might work with people I already know and have already interacted with in several different ways, but not people I see posting things online. It makes sense that people get defensive when confronted and may feel embarrassed, but beyond being civil what exactly can you do? I don’t think it helpful to the general population to allow conspiracy theories to stand unopposed. This is dangerous. I do try to avoid attacking the person, but some see any direct opposition to falsehoods as a personal attack. The experts suggest – If it is bad, stop. Not advice I find helpful. If someone claims that Biden was not actually elected as the President or that COVID is a hoax, you cannot stop even if you don’t change the mind of the person you find yourself contradicting.
Anyway, the article I link offers an honest assessment of this situation and it offers both suggestions and links to other resources. You can probably determine my suggestion. Be firm in focusing on facts and valid sources. Ask questions and invite a defense of reasons you believe cannot be supported. Don’t agree to disagree on settled science or obvious falsehoods.