Okay, have about this:
"maybe the increase in earthquakes is due to all the cars heating up the earth's crust".
No the person who said this was not stupid, just had an INCREDIBLY bad grasp on science. I patiently tried to explain that the Earth's crust was more than 3 km thick, that no amount of heat generated by an amount of cars could possibly be conducted through the earth's crust and even if it was, the earth's interior was millions of degrees so it would amount to beans.
I also explained that there wasn't an "increase" in earthquakes - it's just that the Earth goes through cycles of increased tectonic activity, and that before they were born there were even MORE earthquakes.
Despite all that she refused to admit they were wrong, and instead got angry and said I was insulting her. All because I said "you haven't been alive long enough to accurately judge whether or not the Earth is experiencing an increase in earthquake activity", and she took this to mean I was calling her stupid.
At that point, what can you say? I had physics on my side, but when the other side doesn't WANT to listen to physics, there's nothing you can do. I suspect this person knew she was wrong, but refused to admit it due to pride.