They're not wrong. Humans have many ways to display loyalty, and belief is one of those ways. This is also why facts can't change these kinds of beliefs (and in fact usually backfire https://en.wikipedia.org/wiki/Belief_perseverance).
Our evolutionary heritage is that shared belief and social unity (even when it's wrong) trumps independent thinking for group survival in a hostile landscape.
> as of 2020 most researchers believe that backfire effects either are unlikely to occur on the broader population level, or only occur in very specific circumstances, or do not exist
from your link
I will go one step further. There are several evolutionary anthropologists that think the number 1 thing modern humans have over other homos that caused us to outlast them is not intelligence, or brain power or physical power, but that we are just more social. Being social it seems is our superpower and our greatest strength but the other side of the coin is that it is also our weakness.