In general the biggest "danger" for a science or field of study in the early USSR was that it might imply that the Communist Party did not have a monopoly on understanding the dynamics of how to run a state. So sociology, for example, was not banned but was totally politicized, totally in line with official party ideology, etc. — the social theories had to flow from Marxist-Leninist thought, and never the other way around.

This was codified with the philosophy of dialectical materialism, which said, among other things, that basically any science could talk about its own domain of study (biology = living organisms and cells, for example; physics = atoms and particles and etc.), but that none of the truths from one domain could affect "higher" domains like politics, social interactions, etc. So a biologist who said, "ah, my study of cells and molecules has real implications for how society is organized!" would be doing so at their peril.

OK. So the case of cybernetics is a complicated one. In the first instance it was denounced as bourgeoise, as a means of either automating a workforce, or a means of allowing engineers to suddenly start talking about the running of politics. Neither are things that worked well with early Soviet philosophy — it seemed anti-worker and anti-Party. So that is something that got it banned. Cybernetics was, in its moments of maximum hype, meant to be a single science to literally rule them all. To do that would put it in a position of conflict with Soviet ideology, where power and knowledge flow specifically from Marxist-Leninist thought.

It should be said that the Soviet Union was not monolithic over time, and neither was cybernetics. In later years cybernetics was rehabilitated and made a tool of the state, at times hyped as a means of merging engineering and Communism. So it's a complex story.

The definitive history of Soviet cybernetics is Slava Gerovitch, From Newspeak to Cyberspeak: A History of Soviet Cybernetics (MIT Press, 2002).