With this response, the approach I've had success with is differentiating between "school gym" issues and "meteor" issues:
If the discussion is about whether to pass a county sales tax to finance a new gym for the local high school, yeah, of course you want other views, and of course you should be respectful to people who disagree with you on that issue. It's fine -- good, even -- to have all opinions represented.
But if the discussion is about whether to stop the meteor headed for the planet, the "let it hit" and "the meteor doesn't exist" caucuses should be shouted out of the room, because that bullshit will kill people. Opinions with lethal consequences don't get the same respect dissenting opinions on more mundane issues do.
Then explain how the meteor is Covid, how the meteor is climate change, how the meteor is invading Iraq on a lie, etc.
With this response, the approach I've had success with is differentiating between "school gym" issues and "meteor" issues:
Then explain how the meteor is Covid, how the meteor is climate change, how the meteor is invading Iraq on a lie, etc.