Dr Neander: The issue is not whether 90% of history is eyewitness or second hand or third hand. The issue is how much weight to attach to it and how much it proves. You yourself have expressed skepticism of some of the "eyewitness" claims concerning Auschwitz (Ms Zisblatt). According to your reasoning, historians cannot doubt eyewitness testimony. But of course, they do. It's a process of judgment, concerning what to believe, what not to believe, what to put into a narrative, and what to leave out of a narrative.
Generally speaking historians are extremely reluctant to say that something "did not happen." But if they do not believe the evidence, or find the evidence thin, then they make a judgment not to include what they doubt from their narrative.
Take the rapes during the expulsions, or the expulsions themselves. As you know, the Germans compiled many affidavits of these expulsions. I have read these from time to time. Some of the evidence I find compelling, some I do not. I can believe that Germans were lined up and shot -- a video of such a shooting emerged earlier this year -- but I do not know how many were shot, why they were shot, and how many died in the expulsions. No one really knows.
The same goes for the rapes. Discussions of the mass rapes of women -- not just German women, but Polish women, Hungarian women, and even Jewish women -- has been "exposed" since the 1960's. As you know, right wing Russians dispute these rapes, because it reflects on the honor of the Red Army. I myself have known some of these women who were raped. One, crippled by the event. I do not doubt in a general sense that this happened.
BUT. One cannot simply say because there's lots of evidence of the rapes (nearly all of it oral testimony) how many rapes took place, that every single rape story is true, why they took place, and so on. The responsible historian can only report the phenomenon, record various estimates, and perhaps quote some testimony that he or she finds compelling. As it happens, the testimony for women being raped by the Red Army has more of a ring of truth than testimony about turning concentration camp inmates into sausages.
But perhaps you disagree, and that is fine. There's much more judgment in history than "irrefutable" fact.