Many things that people believe are ridiculous. People used to think that if a woman ate strawberries it could make a baby be born with a birthmark.
Ridiculous belief? Yes.
Ridicule the belief? Bad idea.
Why? For much the same reason as Londo mentioned above.
Another reason to show respect is because to not show it involves me judging the individuals who hold it.
It sounds good to say we wont/dont judge people, just beliefs but I find that not to be the way it works in real life.
At some point, if an individual chooses to stay with a belief deemed "wrong" the judging happens.
That is a slippery slope - judging another. It begins to effect who you are yourself and not in a good way.