The Tea Party sure are crazy. Anti GMO nutters tend to be of the left though, and anti vaxxers commonly are too. As for history, I'm not sure if it's as common now, but you used to hear a lot of denial about the conditions in soviet russia, cuba, etc.
I think for a majority that identifies "left", that the evidence currently supports a lot of their views is merely a convenience. Lets say we magically start heading to the left policy wise, and a few years later some studies come out suggesting we're spending too much on public education or welfare or whatever else. The majority of the denialism will come from the left, some may believe the studies but believe we shouldn't fix the problem because it will be a slippery slope, some will discredit them, some will never believe them even if the evidence continues to pile up.
I say "magically" because I totally agree with you that we're way to the right of where we need to be, and I can't see the direction changing without the shit hitting the fan in some major way, probably beyond our lifetimes. My point is just that I think it's more important to identify with evidence and determining what works and what's right than with any particular broad political movement.