I certainly don't think that reading opposing viewpoints is a bad thing--far from it. I just don't think it reasonable to assume that the truth lies halfway between them. Moreover, not all histories are of equal quality, though one would hope that using the judgment that one need not be a historian to acquire, one would be able to tell the difference. Critical reading is, as you say, essential, though I'm not exactly sure why you think it's any less essential for historians...

How interesting! I doubt it's ever been translated too, but that's a pity for those of us who don't read Polish...