Ignore is the only option. Any time someone's throwing out anything that clearly indicates they're not interested in facts or research, engaging with them only wastes your time and emboldens them (this applies to plenty of other nonsense, of course).
I do try to see if anyone I know is engaging with them, and talk to them directly, but allowing the conversation to continue just validates it.
Like this:
https://m.stacker.news/25201
This is the answer for most of the nonsense they throw at our heads.
Ignore is the only option. Any time someone's throwing out anything that clearly indicates they're not interested in facts or research, engaging with them only wastes your time and emboldens them (this applies to plenty of other nonsense, of course).
I do try to see if anyone I know is engaging with them, and talk to them directly, but allowing the conversation to continue just validates it.
You don't need to respond them.