I swear, every single time this happoens, that you talk to a stranger for a wee bit longer, when you ask them about things that are important to them, they turn out to be wonderful and intelligent people.
And now you say "Yes, but talk to anyone long enough and they'll show their true colours in saying something mindblowingly stupid."
What, you've never said anything stupid? You've never been wrong in your entire life? You never changed your opinion when you learned differently or simply saw more of life?
That's the secret to people: we're built to strive for awesomeness, but none of us are perfect, so it's totally up to you, the person asking the questions and listening to people reply, to decide which bit you choose to concentrate on: the bit that doesn't know better, had a bad day or hasn't had the exact same life experience as you've had or the one that's just like you.
Scary, eh? :D