People believe what they want. Ergo they side with the people who state that those beliefs are true, makes them feel good. Listening to experts who know better and oppose the held beliefs makes the believers feel bad, ergo they won't believe them.

Sometimes it is good to disregard the opinion of experts who are absolutely sure something can't be done, might by a prerequisite to making it happen.

The four minute mile comes to mind.

Beliefs are powerful, they can enable you to reach goals, become prisons of the mind trapping you or become delusions when feedback is disregarded.