The Armenian genocide, the Nazi holocaust against Jews, the killing-field genocide in 1970s Cambodia, the Tutsi-vs.-Hutu Rwanda slaughter of 1994, the Serbian ethnic cleanings in the early ’90s — these are some of the greatest genocidal hits of the last 100 years. But the impending slaughter of Iraqi Christians and Shiites by the ISIS nutbags will surely rank as one of the most horrendous ever. And yet the “wise” and “prudent” course is to let the ISIS genocide run its course, a lot of people are saying. Let the Iraqi factions thrash it out. Roadside executions, beheadings, crucifixions, female genital mutilations…all of it. Let the evil spread and find its own level. If only the country could be split into three natural portions, which is what Joe Biden has been saying for some time — Shiite, Sunni and Kurds.