Money, like religion, is one of those subjects that makes many people uncomfortable because it can trigger some very deep-seated anxieties. I've seen the visceral reaction to Bitcoin you're referring to and my theory is that it's a fear response. They're afraid to invest because they're afraid of losing their money and even worse, feeling like suckers for taking a bath on "fake digital money." But they're also afraid not to invest and missing out on an absolutely huge opportunity. If the first fear wins out, cognitive dissonance makes it important to convince themselves they've made the right decision - to keep the second fear at bay. That cognitive dissonance can make them react in what seems like a weirdly-hostile manner to pro-Bitcoin arguments.