This week's standout in the Denies-Established-Science category, of the ones I've dealt with, is CNN911Fakes, who dismissed the concept of the partial pressure of gasses (Dalton's Law) - which he had apparently never heard of until I tried to explain to him why 4 psi of oxygen is a life sustaining atmosphere.
I'll leave off the lead-up and skip straight to the fun part.
The truth is, any ambient air molecule, regardless of kind, is pushing on your skin at the same pressure as all the rest of the ambient air molecules.
To say that the oxygen pressure at sea level is 3 psi because oxygen makes up 21% of the ambient air is what is twisted and just plain wrong. Every oxygen molecule pressing against you is being pressed there by all of the rest of the ambient air molecules.
Of course, this is also one of the same guys who insists that rockets can't work in space because they have a "big honking hole" at the back, so the vacuum of space would suck the propellants out before they could ignite.