Stalin good actually, but best not to bring it up with the Tatars or the Ingush. Also the song about Stalin in the Tractor Drivers maybe a little cringe. All literature published in the English language covering the prewar Soviet Union, especially academic literature, must contain a ritual denunciation of Stalin. If you want to engage directly with the bases for these denunciations, that is a little harder to research.

It's important to understand that Khrushchov's "secret" speech denouncing Stalin in 1956 was an enormous contributing factor to the Sino-Soviet split, which became more or less official that year. The image of Stalin represents anti-revisionism to the communists who use it today. Stalin's bust is a symbol for the rejection of the revisionist turn in the postwar Soviet Union. It is also stands for staunch opposition to Trotskyism and Maoism. You will find however that communists rarely deal in absolutes. Dialectic analysis of history allows for simultaneous acknowledgment of the bad and celebration of the good in any person or political project.