Reminds me of a talk I had with someone about evolution. I pointed out that you can see birds or bugs that are clearly related to eachother but different, they said those were just microchanges and that didn't prove anything, and I pointed out that those microdifferences would snow ball over time. Apparently no one had explained it to her in that way because she immediately had this look of genuine distress like her entire worldview had just come crashing down.