The layout of textbooks, I think, has been done with an assumption that students don't read.
Nobody would ever want to read a textbook about the Civil War and then interrupt that for two pages about water rights in the west.
Conclusions are not always pleasant.
Those who don't remember the past are condemned to repeat the eleventh grade.
History can be a weapon, and it can be used against you.
Textbooks should show that neither morality nor immorality can simply be conferred upon us by history. Merely being part of the United States, without regard to our own acts and ideas, does not make us moral or immoral beings. History is more complicated than that.