Whether or not anyone believes the statement to be accurate, it is simply not cool to misquote someone or to attribute a quotation to someone who did not make the statement. It does indeed matter very much who said it in the sense that it is wrong to attritube to someone something they did not say. How would you like it if someone did that to you?
By the time the Soviet Union fell, Stalin and his brand of communism had been dead for a few decades. People who had believed in him had lost faith in him long, long before the Soviet Union fell.
If you believe 'intellectuals' created fascism, communism, socialism and every other 'ill' of the world, every other philosophy, that would suggest to me that you believe anyone who reads, writes, thinks, and is educated is part of some evil entity in this world that falls under the umbrella of the term, as you define it "intellectual." Jesus would, therefore, also be an intellectual. In fact, Jesus was a socialist and an intellectual. Hmmmm.....
I imagine Churchill used the term genius, when he spoke of Mussolini, in a political sense. It is not the same thing as being an intellectual.
Porter did not write his song about Mussolini. P.G. Wodehouse was a satirist, which means he was being satirical in changing the language in the song to include Mussolini.