1938? Really? Of course neither John Q. Citizen or anyone else knew about experimentation and the ovens then as
such doings weren't even going on then!!! The murder of Jewish civilians started in Poland with the onset of the war and they certainly were vigorously pursued thereafter in a more ad hoc basis, but the modus operandi that we're talking about here didn't really start until much later. You have heard of the Wannsee Conference, that codified the systematic programme of transportation throughout the continent and the means of efficacious disposal at the end of the line, haven't you? While it also dealt substantively with the SS as being the lead dog in the process and the effective definitions of who would be Jewish enough to be drawn into the horrors, this was the setting that really got the ball rolling for the mass systematic execution of these dictates as we think of them today. The date of the conference? Jan. 20, 1942.
Again, I would say that it is clearly documented that the President himself, as well as many members of his cabinet were aware of what was occurring long before any camp was actually liberated. Hence the continuing academic, moral, and ethical debate over why certain actions may or may not have been decided to avoid taking, that would have had some impact on the eventual totality of the attempted genocide. Definitely not some vague information privy to the War Department only.
As for Lindbergh, what you didn't mention, and I'll admit not following the link, is that as a scientist he was a noted proponent of eugenics, and while arguably not as virulently antisemitic as the hardcore, not acquiescent Nazi leadership, he did avow that Jews were of a lesser genetic strain. "We can have peace and security only so long as we band together to preserve that most priceless possession, our inheritance of European blood, only so long as we guard ourselves against attack by foreign armies and dilution by foreign races". As appeared under his hand in Reader's Digest in 1939. Roosevelt himself claimed his surety that Lindbergh was a Nazi in all the salient meanings of the term. As for his strenuous arguments about keeping America out of the fray, it wasn't because of fear of defeat, but that the US had no fight with Germany, nor should have Great Britain. "I was deeply concerned that the potentially gigantic power of America, guided by uninformed and impractical idealism, might crusade into Europe to destroy Hitler without realizing that Hitler's destruction would lay Europe open to the rape, loot and barbarism of
Soviet Russia's forces, causing possibly the fatal wounding of western civilization" (Lindbergh's autobiography). Hardly the apprehension of someone that fundamentally saw a justification in going to war with Germany, rather than actually holding them up as an ally to look up to and a bulwark against inferior hordes.