1. I don’t think it is justified to execute thousands of people for the sake of such an experiment.
2. The USSR regime under Stalin experimented collectivisation of farming.
3. Thousands of large farmers renserved it and were imprisoned, depored and even put to death.
4. Ordinary democratic liberties were denied to the citizens.
5. They have done away with any opposition through the use of force including large scale execution of opposition leaders.
6. Rapid construction of economy led to poor working conditions, workers lived hard lives.
7. Many intellectuals and others horrified by the violent elimination of opposition and denial of multiparty democracy and freedom in the USSR.