They move from chem trails to moon landing conspiracies...its just insane and impossible to have a sane discussion with them.
They refuse to listen to facts and use due diligence to do a fact check and just fall back on layers of logical fallacies.
I've dealt with a few and have just given up and cut ties and wish I had done it sooner and not wasted my time in the first place.
TLDR: I agree get way quick there is no hope for them when they start evangelizing.
I have a first cousin like that. Very smart, high IQ, but you just can't reason with him. There is no hope. Best course of action is to agree to disagree, keep contact to a minimum and move on.
Cousin refuses to visit doctors/hospitals for "reasons". Never been to a dentist and refuses to use toothpaste to wash teeth "because of the chemicals they put in there to dumb us down". He has now lost 2/3 of his teeth (even some front ones).