There are elders in the family who send spam in the group every day, and send spam every day when they open it.

First of all, you should use science to break the pseudo-scientific mentality. Either you directly challenge him, but it is estimated that you have already tried, and it has no effect. Or he sends an article and you go to find an article with scientific argumentation to hard him with facts, but this is time-consuming and laborious. In fact, you just need to tell your family that what he said is pseudoscience, just like some people believe in geomantic metaphysics and are stubborn. If you don't believe it, you can't convince him.