Something that frustrates me about most historical fiction is that the hero is almost always out of place and time. The hero and his companions act and hold beliefs like a modern westerner, even when everyone around them doesn't. Even when the belief was so ubiquitous that it was held by 99% of the population. Somehow, your hero is always in that 1%.
This is even worse in RPGs because they offer you a choice, but that choice is usually limited to "be nice like a westerner" or "ignore it."