Good point. I'd say that for any new information, there does need to be an initial 'smell test' threshold. When confronted with something so outlandish, I typically switch to making a judgment about the person and how their thought processes work. I.e., ask them to explain the basis of their claim and look for overt logical fallacies, which we all get better at identifying over time.

It's also got to be a matter of sufficient consequence to be worth the time.