If there was a chance they really believed it, and that very belief had a chance to destabilize the country, I'd take it very seriously.
No, but I'd be polite to them and ask them how they know that. Like I just did. Maybe you can learn something from that.
Donald Trump himself wasn't a politically viable candidate until people took his transparently bad faith, virulently racist birther lies in good faith. Have we learned nothing?
Wait the moon is not made of cheese? Where does cheese come from? Why did we go to the moon then?