The best is when someone tells you that 100 scientists agree on it, so it must be true, but it turns out that a few claimed it and a bunch of other scientists back them up without actually doing any science.
Don't even get me started on all the fraud we've been seeing lately in scientific journals.
I no longer really fault people that don't believe what a scientist tells them. The ones that make the news are the least trustworthy and usually have some bias towards what they're saying.
If I didn't understand science as well as I do, I'd be tempted to join them in disbelief.