Because, why would a leftist journalist -or college professor- want to tell them.
“For instance, a third of millennials say they believe more people were killed under George W. Bush than Joseph Stalin.“
To correct that impression, knowing a single genocide by Uncle Joe suffices:
The Holodomor (Ukraine, 1932-33, 7 million dead).
Democide: Data collected by Rummel about governments murdering their own people or parts thereof; usually leftist regimes – because they’re economic basketcases. And want Klassenkampf anyway. And the Kampf in Klassenkampf does NOT mean a polite exchange of arguments but the wholesale murdering of 30% of the population – the bourgeousie, which is a decadent European way of saying THE CITIZENRY – as opposed to “the workers”.