There is evidence all over the place that the extermination camps were no secret to anybody. This was known in the earliest days of the origination of the camps..
The pope and the "neutrals" in Switzerland and Sweden were actually complicit in their non-action when the information was made available to them.
What could the allies do about them? Nothing until they physically overran the territory where the camps were located. Eisenhower actually demanded an entire army of eyewitnesses because he knew there would be future denial that this holocaust ever occurred. Stalin could have cared less. He killed as many or more people in his reign of terror.
There was no way anyone could bring social pressure on Hitler to shut down the camps. Speculation on that is just dumb
“The pope and the “neutrals” in Switzerland and Sweden were actually complicit in their non-action when the information was made available to them.”
The Swiss and Swedes, yes. The pope actually was credited by Jewish historians like Pinchas Lapide with saving 860,000 Jews at one time or another. That number may be an exaggeration. But even liberal Jews - who despise Pius XII as a conservative Catholic - admit he saved 200,000 Jews: http://www.haaretz.com/jewish/pope-pius-xii-saved-thousands-of-jews-1.300589
http://www.catholicnewsagency.com/news/jewish_author_defends_pope_pius_xii_in_new_book/
Also, Pius XII was an active participant in plots to overthrow Hitler knowing full well that those plots, if successful, would mean Hitler’s execution: https://cruxnow.com/interviews/2016/06/17/pius-xii-active-conspirator-three-anti-hitler-plots/
Nice trick with trying to slime the Swedes and the Swiss.
Exactly what two small nations of around 3.9 million each could have done against Germans with its 78 million and 7 million extra eastern European Volk-deutsche? Gone to war? Both nations were holding their breath hoping to avoid being taken over in 1940 through mid 1943. I suppose they could have gone to war something in 1944, but at that point it did not matter, Germany was defeated and exactly why these small countries should be compelled to kill their young men for a predetermined cause escapes me.
When one is weak(both were)and unable to protect others you are not complicit when a local bully is beating someone up and you know about it.
Also there have been volumes written on the degree to which the nature of the camps was known and unknown. There is grounds for questions. The Nazis went to great extents to allow folks to have sufficient grounds to believe it was not so, that the Jews were being settled in the east, not killed. All sorts of fake things like mailed post cards and the like.
Certainly sometime in the summer to fall of 1944 it seems to truth was known in the west and likely in both Sweden and Switzerland, but by that time most of the killing was done.