It was a poorly worded question... I mean it's pretty tongue in cheek to start with, and as brownfist mentioned, Marx had a genuine desire for human liberation, so from that perspective, the Church is out. Thinking a bit more about it, I have more in mind actual communist regimes, say, Stalin's for example.

But I should have specified that I'm just fucking the proverbial dog... I was thinking about why authoritarian regimes would not use existing oppressive structures rather than combat them. In the end, I'm down with the opium analysis.

poetofthefuture did bring up liberation theology, and along that line, I was also thinking a bit about the United Church's social gospel that led to the creation of the CCF and the NDP as progressive examples, but that is kind of besides the point.