Inel has a dispiriting report on Lindzen managing to confuse non-experts over climate change, even with an actual scientist there to correct him. I wonder if it's an artifact of the "debate" in that nonprofessionals see two experts debate and therefore conclude there's something real to debate.
Still, I'd wish that when people hear someone proclaim that virtually everyone else involved in the scientific field is wrong, then either he's a lone genius or a quack. And he'd have to be quite a genius, because you'd expect the genius would be able to persuade the brighter of the non-geniuses in his field to believe him. So he's either so far above everyone else in his field that they can't comprehend him (note that didn't happen with Einstein), or he's a quack. If you're a non-expert trying to make a policy decision that depends on science, I'd say the odds are in your favor if you put him in the quack category.
Also, I'd at least expect a genius to explain his theories rather than mislead people about it.
For other ideas on how non-experts can judge experts, here's an previous attempt I had on the subject.