What did the Soviet Union not like about democracy and why did they feel that way?

It might be worth asking a related question to the one you've posed: Was the Soviet Union actually as ideologically opposed to democracy on its own terms as we tend to assume? It's an interesting question, and one worth thinking about in and of itself. If you've ever read the novel Darkness at Noon, this is actually a theme that comes up in its treatment of Rubashov, who was himself a stand-in for the first generation of Bolshevik leaders (later betrayed by Stalin, sacrificed to the Revolution). What we see depicted in that book—and I think it's frighteningly accurate to history—is an undercurrent of pragmatic calculation by which the Party demands sacrifice in the name of the Revolution, all for the supposed purpose of creating a future utopia (and this is a key theme central to understanding Marxism: it's ultimately utopian in its aspirations). This raises the question: if the single-party dictatorship is understood ideologically in terms of being a means to utopian ends, could that future utopia itself be democratic?
In any case, I would suggest that one of the critical issues here is the degree to which Western democracy has historically been tied up with capitalist economies as well as imperialist exploitation. This means that communists would certainly have found much to be suspicious about, as far as Western democracies were concerned. Furthermore, consider the history of the Bolshevik Revolution itself and the degree to which Western democratic powers interfered by supporting the White Army. Of course, Western powers had reasons to distrust the Soviet Union as well given its internationalist vision of communism and the vocal internationalism represented by someone like Trotsky, who argued in favor of global revolution. Both sides would have pictured this in terms of an ideological clash between the liberal powers of Western Europe and the United States on one side and the communists on the other.
As one last subject worth thinking about, I'd suggest you factor in the ideological split within Russian communists. While the Mensheviks believed that the movement should be populist in nature, the Bolsheviks believed it should be driven by a professional elite dedicated to the revolutionary cause. Naturally, it was the Bolshevik position that ended up shaping communist Russia, and once the Bolsheviks took power, this elitist vision of the revolution resulted in a very hierarchical political structure by which power and authority emanated from the Communist Party.