'ignores scientific consensus'. https://en.wikipedia.org/wiki/List_of_superseded_scientific_...
'promotes speculative theories without empirical evidence'. Haven't Peter Woit and Lee Smolin pointed out how String Theory does exactly that? Have their criticisms been made redundant by more recent research? I have no idea but maybe a physicist would care to comment.
No sane flat earthers in this day and age actually believe the earth is flat, or deserve to have their presumed beliefs respected or even humored, because they're just being contrarian and trolling for attention, so it's perfectly valid to say to them "FYI, the Earth is not flat."
I refuse to couch my firm disbelief that the Earth is flat as an opinion that might possibly be wrong, by saying "IMO, the Earth is not flat." Flat Earthers (also Young Earthers) certainly aren't couching their crazy beliefs as opinions, so don't deserve it in return.
"Chariots of the Gods?" is also that objectively wrong: there is no possible universe in which its claims are true. It's all based on historically ignorant Argument from Incredulity and inherently racist assumptions. In the 50th anniversary edition, von Däniken refused to address, admit, or correct any of the many widely proven errors in the book that made him so much money and fame, so he doesn't deserve to be taken seriously.
https://en.wikipedia.org/wiki/Argument_from_incredulity
Believing in pseudoscientific claptrap like Homeopathy, or the objectively false stories of Adam and Eve or Noah's Ark is just as ridiculous. They're physically and mathematically and logically and practically impossible. So it's also fine to say "FYI it's biblical fiction, and the Earth is definitely not 6000 years old, and you absolutely can not fit and feed and clean that many animals in a wooden ark." It's not my opinion, it's objective information.
https://www.youtube.com/watch?v=F4OhXQTMOEc
To pretend otherwise feels like humoring a small child who still believes in Santa Claus.