Always remember that the burden of proof lies on the claimant. Furthermore the burden of proof is, in some cases, due to more people than the one we put our claim onto.
Jack: Earth is flat
Jill: that's not true, science proved it multiple times
Jack: oh really, prove it
Jill: you prove it, and not to me, but to thousands of scientists whose proofs you don't ...
I've never felt important to me some other people believe things I consider completely wrong, so when I'm presented beliefs in the vein of 'Earth is flat' (I can definitely think of similar claims in some members of my family) I would only address them if they are presented specifically to me.
In the case I really don't have the energy for an argument, ...