Generally speaking how did most communist régime's throughout history view non realist artist, non classical musicians, and writers in society?
In general terms, avant-garde art in China and the USSR (but not in Cuba) was criticized for being bourgeois: it was not easy to understand, it did not praise the virtues of the people, and it did not help promoting the state.
This being said, avant-garde art had been welcomed in Soviet Russia at first, in part because non-traditional art was seen as revolutionary. Also, during the New Economic Policy artists faced few restrictions, which led constructivism to thrive. With the advent of Stalin, however, a new heroic, realistic style (Socialist realism) was enforced.
A couple of books on the topic:
Victor Margolin, The Struggle for Utopia
Christina Kiaer, Imagine No Possessions
Matthew Cullerne Bown, Socialist Realist Painting