The anti-vaxxer. The climate change denier. The moon hoaxer. We all know that one person in our family or circle of friends that just won't give it up. And what's worse, it seems like every time you're together that's all they want to talk about. And you, being the strong-willed advocate for science that you thankfully are, marshal your evidence and lines of convincing arguments and attempt to disabuse them of their egregiously incorrect thinking.
And then the yelling starts, somehow.
I get it, I really do. I've been there myself...many times.
But if someone didn't arrive at a conclusion via evidence and rationality, then evidence and rationality isn't going to change their minds. They believe in these things for some reason, but it's probably not a reason that we can a) uncover easily and b) navigate comfortably over dinner.
So what to do? Well in the words of famed English novelist and critic George Orwell, "the quickest way of ending a war is to lose it."
It seems paradoxical, but look at the evidence: if you have never won these arguments in the past then you probably never will in the future, especially when your opponent is bringing up these issues specifically to spark one.
So drop it. Don't fight that battle because it's a losing proposition. Don't try to change beliefs, because beliefs are hard to change. Most beliefs are harmless, anyway. Someone who believes that we never went to the moon may be (extremely) irritating, but it doesn't change what we do as scientists and science communicators. Life goes on, doesn't it?
And where beliefs do cause harm (sending kids to school unvaccinated, voting against important policies, and so on), fight them there. The actions and results of a belief are fair game and should be resisted - on their consequences for everybody else. It's the difference between telling someone their beliefs are wrong and arguing that a result is harmful. People hold strongly to their beliefs...but are perfectly willing to compromise those beliefs when the situation is right.