OOC: Was kind of going for an Iron Dream sort of thing, where due to alternate circumstances communism is viewed as the most evil, genocidal ideology in history, while fascism is seen as largely as a lesser evil or even actively admired and defended.
Did it on the fly, and it's probably not the best, but my rationale was pretty much that Communist Hitler, while not as fixated on the ideals of übermensch and untermensch, is still a rabid anti-Semite ITTL. Stalin, partly due to his own antisemitism and partly due to Hitler's influence, joins him in wholesale slaughter of Eastern European Jews. It's more of a Holodomor than a Holocaust, with forced labor and starvation instead of gas chambers and mass executions.
The genocide of the Turkic peoples was partly meant as Russification gone mad, partly Sino-Uigyhur conflict, partly the fascist British Empire encouraging revolt against communism in the Central Asian SSRs leading to a crackdown.
The "incinerated Persians" wasn't as much an ethnic issue as it was a Soviet invasion of Persia in the 1960s (never changed to Iran ITTL) that saw the usage of nuclear weapons against Persian military and civilian targets.
The Afghan Genocide was essentially a similar issue; not as much a true genocide as the Soviet-Afghan War going far, far worse for the Afghans, with frequent war crimes and usage of WMDs on the part of the Soviets.
In retrospect, it probably wasn't the most realistic (especially because, as you mentioned, Jews had a prominent role in German communism), but again, I was going for a kind of role reversal between fascism and communism in this universe.