angrysoba
Philosophile
I've seen this type of critical thinking in action. A mother tearing a crying child away from a sinterklaas entry into my hometown (a big parade thing encouraging the horrible magical fantasy/hoax which is immense fun) telling her 4 year old "No, there is no such thing and unlike everyone you know YOU will not get brought presents, because its not real!"
I think you're forgetting the third option which is to agree that "Santa Claus" is there in the same way that you would if "Mickey Mouse" were there. I don't see anyone advocating wrenching a child away from "Santa's Grotto" even if you have seen others do it.
Sure, it teaches critical thinking at an early age, and also teaches that critical thinking = sour killjoys who take away the fun things everyone else does get to do.
Actually, I don't think the situation you described teaches "critical thinking" at all. But no matter, because no one here is advocating that behaviour as far as I can see.