I'll test the waters as you did, but if it appears there's cognitive dissonance due to my shattering their little naive world, I keep my mouth shut and move on. I'd rather take the quiet route at that point rather than be mean. I guess like Thumper's philosophy from Bambi....

Too many times I have wasted my breath on what is a lost cause, at that time. Some people will never wake up to what's going on and others will, but only when they're ready. In cases, such as what you stated above, you may have been the catalyst or seed to their eyes opening if they ever will but you will not be able to convince them on the spot. They need to go down that path on their own.