Petra,
It's called Selective Indignation Syndrome (SIS). Funny you should mention Stalin in the context of Castro. I'm just now getting over a cold after spending a couple of days basically in bed streaming my favorite WW2 documentaries. It amazes me how Franklin D. Roosevelt and Winston Churchill were savvy & flexible enough to tolerate Joseph Stalin in order to deal with Hilter's Third Reich. That was clearly an example of enemy-of-my-enemy.
I've often wondered how much the Nazi & Soviet occupation of Poland influenced Castro's decision-making in Cuba. I'm not a fan of his but acknowledge that he was a very astute lawyer who was well in tune with world events prior to becoming a malevolent dictator for life. He would go on to visit Poland and write about the nation several times. We can say or write what we like about Fidel Castro but he did help Cuba retain its sovereignty while the super powers were busy carving up the globe. And sadly, in the wake of the atomic bombings of Hiroshima and Nagasaki, and later the Central American crisis, the US lost much of its moral high ground in the international arena.
After viewing those WW2 documentaries, I'm left with three lingering questions: (1) is it possible for a Hilter or Stalin or Mussolini or Franco to emerge again, (2) what is the free world willing to do to stamp out ISIS/ISIL, and (3): why haven't the 11 million Cubans toppled the Castro regime?
#FactsMatter...your feelings not so much.