Responsibilities for Correcting Woo

[moonsail]

If someone is propagating woo, e.g. "cell phones start fires at gas stations!", to people you regularly associate with, what sort of responsibility do you, as a rational human being, have?

If it's in regards to someone I regularly associate with, I feel both obligated to correct the woo with evidence, but at the same time feel like I'm being a dick for doing so.