This is a great display of kids pushing to be educated and not indoctrinated. Conservatives call colleges liberal training grounds, but back this idea of a sanitized history class? What is wrong with teaching the kids what actually happened?
Instructional time is finite. From this it follows that priorities must be set. Knowledge is not hidden, it's there for all of us to access, and students who have a desire to intimately know American history have a lifetime available to them in which they can drink deep. This though doesn't describe most students. Most students are no social activists, most students simply want to be citizens and they love their country. We want to serve these students by informing them of the history which makes us all proud.
This notion of total transparency in everything is bogus. Do parents reveal to their children the entirely of their sexual history, a play by play of every person they had sex with and all the other warts in their life? There's no need for parents to do that. Similarly there is no need to devote finite precious class time to liberal-inspired hate-fests of where America went wrong, or more precisely, where America-hating liberals believe America went wrong for this entails an opportunity cost of skipping instruction in knowledge that has more utility. The America-hating liberal agitprop is freely available everywhere in society, especially on college campuses. Nothing is being suppressed or hidden, it's just not being celebrated.
One of the primary purposes of public schooling is to impart cultural unity into the student body, a shared understanding of American history, knowledge which will make students patriotic and committed to the nation and fellow Americans. Teaching students to hate America doesn't serve a purpose, public schools don't exist for that purpose, that's why liberals exist, to take over where public schools leave off.