Faith? Just what is it? An irrational belief is faith? Is the World flat or "round"? Some people believe the World is flat. Are they rational?

Now then, explaining to those believers just how we know the World is round and showing them what we know and how we know may just convince them that their belief is wrong?

Moving on to other "beliefs", explaining and showing that each part of what they believe is incorrect, picking each bit apart, point by point may help the situation?