I think Bob should try to get better at explaining.

Got any tips for Bob and the rest of us?

The only stratagem that occurs to me after reading Zed's dialogue is that Bob should have spent more time motivating his solutions. I notice that Rian is the one asking all the questions, while Bob is the one offering short answers. Perhaps if Bob had been asking Rian why someone would believe in the opinions of experts and allowed him to offer possible solutions, and then guided Rian's own questioning in the right direction with more questions, the exchange would have gone differently.

I'm a bad explainer in this sort of situation, too, but perhaps something like:

Rian: That doesn't make sense. It's still just an opinion. Evidence comes from experiments.

Bob: Hmm... perhaps we think about evidence in slightly different ways. So is evidence only something that comes from an experiment? Do you form your opinions using only evidence, or are there other ingredients, too?

Once I've got a positive position staked out from Rian, I can much more easily show him the reasons that I think they're wrong. I'm no longer at risk of appearing a credulous crackpot, but instead appear to be the level-headed skeptical one.

ETA: One more attempt at summarizing my idea: don't offer your solutions until the problems are understood.