Every story has elements of good and bad. We can choose at what time to
end the story (all stories must have an end, simply because of the
limits of time and pages). Weddings and births are just as real as
betrayals and deaths. Good things do happen; people do
noble acts. Giving the bad things power to negate these is
superstitiously giving evil way too much power.
We can chose where on the spectrum to tell the story --
over-pessimistically, over-optimistically, or realistically. And no,
"realistic" doesn't automatically mean "tragic" or "sick" or "evil."
In most cases, realism will lie somewhere near the center of the
spectrum. Yes, there are some cases which are realistically near the
bad end, but by definition these are very rare, for to be at that
extreme end, the bad parts have to be prevalent, and/or extreme -- and
these are comparative characteristics, meaning "more" or "worse" -- than
norm and stand out as unusual against the general
background of the human condition in that era and place.
Holding the beliefs of one's culture (and by "culture" I mean an
longtime, pervasive one, rather than a political or idealogical
subculture joined in adulthood) or acting in accordance to that
culture, however wrong its basic tenants, doesn't make an individual
"evil" or "immoral" or "sick" (or "seriously flawed," the current
euphemism for "evil" or "immoral" or "sick").
Facts must be presented. But wording and emphasis are choices --
choices that tend to say more about the teller (and/or the audience the
teller is trying to please) than the subject.
Wording, emphasis, comparison with an impossible (or exceedingly
difficult) or rare ideal can distort a statement toward an artificial
negative. Consider the following:
"He freed eleven slaves." (A basic statement; it inherently feels
positive, as the verb is a positive word.)
"He only freed eleven
slaves." (The wording adds a criticism of lacking.)
"He freed eleven
slaves, but we must always remember that he owned slaves in the first
emphasis is placed on the negative.)
"He freed eleven slaves, but
another planter freed all of his." (The existence of the greater is
presented as a foil
to negate or diminish the good. In addition, it's presented as if the
two circumstances were the same.)
The problem comes not when there are a few books showing the dark side
of history, or a single unflattering biography. It comes when this type
of history is seen as the only valid view, when every admiring
statement must be offset by a criticizing one.