@altschmerz Yup the guy who wrote that article is simply parroting the Catholic church official line while claiming to be an atheist combatting "revisionist" history.
The facts actually speak for themselves, if all of Cornwell's book is disregarded, Pius DID make a deal with both the German's and the British not to bomb Rome promising both that upon their inevitable victory God and the church would reward them.
He did pursue and gain a Concordat with the Nazi government, He was photographed with and entertained many high ranking Nazi officials including allowing an ambassador from Nazi germany to live in the Vatican in his own apartments an honour not granted to any other countries ambassador.
He did start and run a Vatican radio station (and Newspaper), which praised the Nazi's of Europe and promised the church's neutrality.
After the allies moved troops into (now non Nazi) Italy for the final invasion, Pacelli (Pope) did write to Eisenhower pointing out that an "enlightened" man like the general would respect the papal request that no "Negro animal" soldiers be allowed in to Rome in the occupying forces as this would inevitably lead to cultural vandalism and a plague of rape in the holy city needless to say the request was made public and ignored.
While at the same time he the pope was sheltering both the Nazi ambassador to Rome and the former nazi Ambassador to the Vatican inside the walls of the Vatican, under the law of sanctuary.
Though it is true many Catholic priests and to a lesser extent some bishops and cardinals did help Jews, gypsies, Jehovah's Witnesses and homosexuals escape the persecution in acts of personal bravery and to their great person honour, many others adhered to the Vatican directive of non interference in Nazi policy, and in some cases such Clergy as did follow their conscience were either disciplined by the church or left to their fate at the hands of the Gestapo or SS. It is certainly true that most who did resist official church policy were after the war destined to serve in more lowly capacities for the rest of Pius's tenure are Pontiff, to teach them the import of obedience to the divine will.
Speaking of which it is interesting that the oft spoken of Doctrine of papal infallibility, usually believed to have originated from the middle ages was actually an invention (or at least a massive corruption of existing doctrine) by Pius XII (A scholar of ecclesiastical law) used to consolidate his position and to prevent the conclave of cardinals over ruling some of his more excessive pronouncements, such as for example the biggest, most expensive and lavish Papal coronation ever seen, for his own inauguration, which included being pulled and pushed through the vatican on an 18 foot tall golden throne.

Probably the best place on the planet to do research would be the Vatican Library. I cannot imagine what would be there, hopefully, many books and texts that would clear up historical questions. Of course, we know that the Vatican is one of the most corrupt institutions on the planet.