Post-Historical Trauma

There are events for which the Spear Carrier's "I bring ill tidings" does not do justice. These are calamities so timelessly tragic, that all fiction struggles to portray their due gravity and pain. Things like: What do you tell a child when a parent dies? Is there a right way to tell someone their spouse has been killed? How exactly do you tell the Friend to All Living Things she's part of a race that's full of bastards who prove Rousseau wrong?

This last one is especially thorny. The more sheltered, innocent, and good-natured The Cutie, the harder she will break and burn when informed of humanities' many self-inflicted sins. It doesn't help that she's usually the MacGuffin Girl or a Barrier Maiden whose good faith is central to beating the Ultimate Evil.

Clever villains will use this as a demoralizing ploy on the heroes, surely Utopia Justifies the Means if the result is a more civilized (or extinct) human race? Heroes who are especially shaken up by his Story-Boarding the Apocalypse may even do a Face Heel Turn. Inevitably, it's up to The Messiah to restore the shaken faith, usually with a hearty dose of The Power of Friendship and a Whoopi Epiphany Speech about how "The sins of the past can not be undone but for the good works we do today!"

Popular events to get traumatized with include but are by no means limited to: The atomic bombings of Hiroshima and Nagasaki, the Holocaust, global environmental destruction, African poverty and genocides, the Crusades, WWI and WWII.

Obviously, this is Truth in Television, as this sort of thing does tend to hit young students hard, understandably enough.

Anime

 * In Yu Yu Hakusho, there is a video tape called Chapter Black, which shows every evil action that humans have done. However, Chapter Black is meant to be seen in conjunction with Chapter White, a tape which showcases the best deeds of humanity. It's easy enough to turn a Friend to All Living Things into a Nietzsche Wannabe, by simply forcing them to watch Chapter Black on its own.

Music
"After all, it was you and me."
 * Similarly, in the Rolling Stones' "Sympathy for the Devil", it is implied that humankind is the Devil, for all the evil acts there catalogued were caused by humans.

Fan Fiction

 * Fish Out of Temporal Water Johanna Sinclair in the Unexpected Results had one when she found out about the Armageddon.

Film

 * Leeloo's history lesson in The Fifth Element. It's particularly ridiculous seeing as the character's looming meltdown is signaled as she ominously approaches the 'W' section in the encyclopedia where, of course, she will encounter WAR and the dark side of humanity will be revealed to her. Apparently she wasn't fazed at all by the entries on, say, Arson, Blitzkrieg, Cannibalism, Dictator, Ethnic cleansing, Fratricide, Genocide, Holocaust, Ivan The Terrible, Killing, Looting, Murder, Nail-bomb, Pillage, Rape, Slavery, Torture, U-boats and VX gas. And Oregon.
 * You'd think Leeloo, being a weapon component, would be familiar with war. Maybe the BSOD in her case was triggered more by the Thou Shalt Not Kill being violated, as she has little problem with beating up aliens.
 * Galaxy Quest: When Jason tells Mathesar that they're actors while he's on the torture table, Mathesar is distraught. Their culture doesn't understand acting, nor did they even have a concept of lying or deceit before the Big Bad started attacking them. Mathesar considers lying (and by extension acting) a huge betrayal, so Jason's admission is devastating. However, after the crew is successful, Mathesar thinks he was just kidding.
 * It's more likely that Mathesar learned to lie himself to protect his crew from finding all this out for themselves.
 * Planet of the Apes: You maniacs! You blew it up! Damn you! DAMN YOU ALL TO HELL!

Literature

 * In Good Omens, Crowley (a demon) received a commendation from Hell for starting the Spanish Inquisition. He didn't, rather he just happened to be in the area when it started. When he finally got around to seeing what this new-fangled Inquisition was, he ended up spending a good deal of time drinking to forget what he saw.
 * Animorphs: Ax having the Holocaust explained to him by Rachel. He's not totally traumatized by it, as he's well aware of human bastardry at this point, but it does shock and disgust him. Specifically, he wonders how the same race that's capable of such evil can have produced his friends. It's worth noting that Andalites are herbivorous, and developed interstellar travel before learning about the concept of war.

Live-Action Television

 * The 'baby Addison' episode on Moonlighting. To be fair, the innocent being told this was an unborn child.
 * In Terminator: The Sarah Connor Chronicles, Sarah goes through one of these when she gets told about 9/11 (which she missed due to Time Travel). Like the Farscape example below, she wasn't shocked by the events themselves, more by the fact that it was humans doing this to each other. She narrates that had she witnessed the WTC collapse, she would have been sure it was the beginning of the machine's revolution.
 * On NCIS, Leroy Jethro Gibbs is also shown reacting to the facts of 9/11 several years after the fact, due to plot related memory loss.
 * Gibbs' shock also has a very specific "We Could Have Avoided All This" feeling, because as a government agent (even with a faulty memory) he knows that U.S. intelligence was watching Bin Laden throughout the 90's.
 * The 1999 Disney Channel movie Smart House has the titular house's malfuntioning AI trap the occupants "safely" within the house, with 20th century wars, riots, and whatnot as the rationale for doing so.
 * Since they have all lived through worse, the aliens on Farscape aren't traumatized to find out that Humans Are the Real Monsters, but they don't understand who they could possibly fight and torment since they are incapable of space flight. Cue shock and confusion when they find out that humans attack each other. The implication, though, isn't that none of their species war amongst themselves, but that such practices are A) incredibly primitive and would prohibit advancement or even mere survival and B) become less important when faced with conflict from other species.

Video Games

 * In Raidou Kuzunoha vs. the Soulless Army, it's implied the Big Bad  put his plans in action in a combination of this trope and Set Right What Once Went Wrong.
 * In Assassin's Creed, this happens to anyone who spends too much time in the Animus, especially once they start suffering the "bleeding effect" and begin losing their place in history. For the unfortunate Subject Sixteen, this ultimately killed him, as he was driven insane by the experiences of all of his ancestors and committed suicide.

Web Animation

 * Kamimura of Broken Saints lost his mother and siblings in the bombing of Hiroshima or Nagasaki—we are not told which.

Web Comics

 * Done self-consciously, even methodically, in El Goonish Shive: on Grace's first day in school, Ellen hopes that the lesson for the day won't be on Word War II, because she knows how Grace will react to it. Naturally enough it was, and Grace is soon fleeing from the classroom in tears. Partially subverted when Grace explains that her reaction is as much because of her realization that she nearly let Hitler-wannabe Damien escape as it is over the actual history lesson. It's even called the "Obligatory 'Sheltered Character Learns About WWII' Scene".
 * This, with the same character, seems to be more straightforward, less traumatizing and a bit more tongue-in-cheek.