However, Paarth saved the world....twice.
Okay, so let's extend this metaphor.
Stalin was a bad man, a tyrant, a mass-murderer. However, he also was instrumental in defeating Hitler, once the alliance between the two had been broken. Let's say, for the sake of this metaphor, Hitler and Stalin also genetically modified themselves to be super human killing machines.
So let's say it's now the year 2012, and super-Hitler is back, and is resurrecting dead nazi super-soldiers. You travel to the top of a mountain where an order of monks guide you towards their leader, who they say can help you, and at the top of the mountain you find super-Stalin sitting there. He promises to help you find a weapon that can finally kill super-Hitler, and does. However, after you find this weapon, a group of nazi-hunters you've also been working with comes and tells you about all of Stalin's crimes, how he had participated in mass-murder on par with Hitler himself, and ask you (the only person who can kill super-soldiers without them coming back to life) to kill him.
Do you do it?
Now consider that once you've finally beaten super-Hitler, super-Stalin intends to take command of all the resurrected super-soldiers. NOW do you think it's a good idea to kill him? Consider that super-Stalin and his super-soldiers will live forever, while you, the only person capable of killing them, will die of old age, and once you are gone nothing can stop them. Now do you see why the nazi-hunters want you to take care of him so bad?
Yet at the same time, the Prime Minister of the UK is trying to secede from the EU because the EU President signed a treaty with the recently succeeded French banning the worship of Jesus while allowing French soldiers into Britain to enforce the ban. The same guys who think leaving Stalin alive with an army of super-soldiers is a great idea think that this Prime Minister is a racist power hungry maniac who should be shot. MAKES PERFECT SENSE.