There are strong minded people and there are weak minded people. Weak minded people can be persuaded into believing almost anything.
I think we can all agree that more people are weak minded than strong minded. Maybe it's 60-40.
And remember. Some people have a belief system because they truly believe it and those people are going to live by that system no matter what. You see that in Conservatives or Liberals or Communists and with Born Agains and with nuts like ISIS. No matter what you say to them nothing will change their mind.
Others are complete dummies or uneducated or easily influenced and they can be put off-balance by a leaf falling on their shoe. This is simply human nature.