If there's a pervasive belief people have is that once they make up their mind about something or someone, _that something or someone_ will never change.
This is likely rooted in that the human brain is optimized to use only as much energy as absolutely necessary–making it really hard and awkward to change opinion, even when presented with a barrage of subjective experience and objective, hard facts.
It's much more convenient to blame the messenger or ignore things.