Experts are wrong on a regular basis.
I would also point out that conspiracy theorists ignore experts as well when they disagree with the "clear evidence" of a conspiracy. I was a SAC crew chief but I've been told I know nothing about planes because I don't believe Flight 800 was hit by a missile. Truthers will tell you that firefighting experts who describe the way the towers fell because of steel being heated by a jet fuel fire are shills for the government. I've watched moon landing conspiracy people be shown that they couldn't possibly be correct that Apollo photos were faked, and ignore it, moving onto the next piece of "proof" that we never landed on the moon.
In the real world, it comes down to proof.
No, they're not...but those who argue by cliche' do seem to move in that direction. Furthermore, when multiple experts agree, only the truly myopic or duplicitous breezily dismiss their testimony.