The archbishop didn't know all the Pope knew. The Pope had his reasons to remain silent, mainly the protection of Church property and influence in German-held lands; also, the old Christian dogma that the Jews must suffer down through history, to prove that they had guessed wrong on Christ, and must one day acknowledge him. ...Wouk gives both of these lines to sophisticated characters, insiders in Italy and Vichy France, whom we are meant to regard as experts. No rebuttal is offered at the time these statements are made, nor is a more sympathetic view of Pope Pius conveyed anywhere else in this widely-read novel.
"Europe is a Christian continent, isn't it? Well, what's going on? Where's the Pope? Mind you, there's one Catholic priest right here in Marseilles who's a saint, a one-man underground. ..."
Of course, Wouk was writing in the mid-1970's, when Rolf Hochhuth's play The Deputy was recent and still riding high as the intellectual's default "understanding" of the subject of Pius' wartime conduct.
And yes, it's "only" a work of fiction. But does that really mean that in creating an imaginary narrative, an author has no responsibility to find out the truth, and tell it? Or at least to avoid character assassination?