

I usually just say “I’m not superstitious” or “That’s not for me” and leave it and my level of involvement with their beliefs to my audience’s interpretation. As for your friend’s partner and your complicit friend, “Those who can make you believe absurdities can make you commit atrocities” - Voltaire.
The condescension and man-splaining thing is difficult and is definitely a trained part of a male-dominated culture/sub-culture if it is based on prejudice. The chainsaw incident might have come from a genuine place of concern and caution since power tools can be dangerous, even variants of tools somebody has experience with. I personally struggle with gauging my expectations of how familiar any random person would be with something I’m bringing up, especially if it’s something I’ve had other people confused by in the past. I usually say “Have you heard of X?” or “How familiar are you with X?” to try to avoid either scenario of my audience thinking that I’m condescending them or them being lost about a subject they know nothing about.