The problem is that strongly-held myths can still cause a lot of harm to others. While it may be understandable for people to cling to some myths, we should still work to stamp them out, but compassionately.
> That's a matter of philosophy and opinion, not established fact.
If one takes “myth” to mean something that is itself believed without being falsifiable, it is true by necessity of any belief system with any content beyond statements about the subjective experience of the believer