It's common, the defensiveness......and is often a knee-jerk reaction that happens very close (time-wise) to the discussion at hand.. Their beliefs are being challenged, even if you are polite.
Hopefully, in retrospect, they may see that you were merely asking sensible questions, or trying to have a constructive conversation.
If they indeed claim to "not be a conspiracy believer"......the fact that they now feel like someone is suggesting that they might be one (on a particular subject), brings up the defensive walls. They feel slighted, accused, or insulted.
I think most people have several unverified beliefs
https://www.metabunk.org/threads/bunk-you-are-willing-to-live-with.1635/.....and we should not expect everyone to research each-and-every one of their beliefs -- ready to hand-out verified references with the click of a button to anyone who might happen to ask.
In a perfect world, maybe.....in reality, not likely.
When I may question a friend's beliefs, I like to tell them that it's 'because I'm interested in their subject' and, "I would love to read some information on this, do you have any ?" (both would be true)......instead of the abrupt "pics, or it didn't happen", or "if you don't have any evidence, your idea is wacko". (extreme example)
I had an idea for a skit for the cable show "Portlandia".....(the alienation of a know-it-all)
External Quote:
a decent idea for a short film......"A brainy-logical guy (or girl, or couple) tries to mingle at a party. But when talking in the party's various group conversations, he poo-poos and corrects each and every lighthearted convo.......adding comments like ...., "but that could never happen" .....and, "studies concur that what you are proposing is in reality, the exact opposite". Within an hour, he is standing alone in a corner, staring at the cat, who's staring at the goldfish in a bowl. Wishing he could speak Felinese - he wants to tell the cat, "...that fish is called Carassius auratus auratus".